ICTON invited presentations:

Alex Alvarado
Regular perturbation for the weak dispersion regime
V. Oliari¹, E. Agrell², and A. Alvarado^1
1Eindhoven University of Technology, The Netherlands
²Chalmers University of Technology, Sweden
The nonlinear Schrödinger equation (NLSE) takes into account the attenuation, the second order dispersion and the Kerr nonlinearities. No analytical solutions are known, and thus, approximations are required. In this paper, we approximate the NLSE by the regular perturbation on the second order dispersion. With this approximation, it is possible to represent some nonlinear regimes with high accuracy.

Muriel Botey
Non-Hermitian broad aperture semiconductor lasers based on PT-symmetry
M. Botey¹, W. W. Ahmed², J. Medina¹, R. Herrero¹, and K. Staliunas^1,3
1Departament de Física, Universitat Politècnica de Catalunya, Spain
‎²Division of Computer, Electrical and Mathematical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
³Institució Catalana de Reserca i Estudis Avançats (ICREA), Spain
It has recently been shown that arbitrary non-Hermitian optical potentials based on local Parity-Time (PT-) symmetry may allow the control over the flow of light, due to the asymmetric mode coupling. We now provide a comprehensive analysis on how this can be applied to stabilize the emission from broad aperture semiconductor lasers, while concentrating the light into a bright and narrow output beam.

Clara Catanese
A survey of neural network applications in fiber nonlinearity mitigationms
C. Catanese¹, A. Triki¹, E. Pincemin¹, and Y. Jaouën^2
1Orange Labs, Lannion, France
²Telecom ParisTech, Paris, France
Advance in optical transmission towards higher bit rate and denser spectral efficiency is challenged by nonlinear effects. The existing digital signal processing techniques to compensate nonlinear fiber transmission impairments suffer from heavy computations and require the knowledge of a large number of system parameters, which is impractical in field environment. Neural networks are among the investigated solutions in literature to cope with the complexity of those models. Taking advantage of the huge amount of data available in optical transport networks, WDM systems represent a fertile field to apply neural networks. This paper is a non-exhaustive survey on neural network applications for nonlinear impairments mitigation in optical fiber transmission systems. We distinguish two approaches. The first one is dependent of the non-linear Schrödinger equation (NLSE) while the second one is based on machine learning techniques. These two approaches achieve similar performance compared to the well-known nonlinear mitigation methods with reduced computational complexity.

Peter Cochrane
Networks for an infinite service future
P. Cochrane and M. Abdel-Maguid
University of Suffolk, Ipswich, UK
Only 50 years ago network design was dominated by well defined, characterised, and understood services, but the launch of mobile services in the 1980s brought that era of certainty and stability to a rapid close. Not only where mobile users different in their habits, they discovered TXT! At almost the same time the internet and dial-up modems were introduced, and these compounded the situation further. Since that time network designers have been largely guessing as to what services they should accommodate and when. The real culprits of chaos here are accelerating technologies and the new services they engender. For example: Facebook did not exist 15 years ago; WhatsApp 10 years ago; Snapchat 8 Years ago; whilst Video/Audio downloading and streaming were not mainstream just 3 years ago. And waiting in the wings we have the IoT and AI services. Needless to say most networks and network designers will continue to be wrong footed by the pace of change! So, what do we know for sure? 1) Video + Audio Streaming will see rapid growth. 2) Video conferencing will eclipse ‘telephone/audio’ modes. 3) The sociology of people will be eclipsed by the sociology of things. 4) 5G will not be the panacea that the mobile industry thinks and/or presents. 5) Auto-immunity has to become a primary mode for the cyber security of everything. 6) The IoT will see more things in disconnected mesh-nets than connect to the internet. 7) Mobile devices are most likely to be overtaken by wearables including health monitors. 8) Robotics and new smart materials harbour many new emergent demands and properties. 9) Information and experience sharing by people/machines to become the new social revolution. 10) We have to strip out the electronics from our networks to achieve green/sustainable solutions. 11) Our networks have to become intelligent/sentient to service the new demands and survive. This short-form (sample) list can only be interpreted in one way! We need networks that are ‘low’, ‘flat’, basically simple and devoid of unnecessary protocol and coding stacks with an ability to accommodate almost any signal and service demand dynamically and intelligently. The dynamic complexity of future demands can thus to be offset by our network infrastructures and solutions.

Ivan Djordjevic
SDN-enabled adaptive modulation and coding in hybrid C-RANs
Mingwei Yang, H. Rastegarfar, and I. B Djordjevic
University of Arizona, Department of Electrical and Computer Engineering, Tucson, USA
In this invited paper, we describe our recently proposed software-defined networking (SDN)-enabled, adaptive resource allocation framework, including hybrid signalling schemes, for mobile fronthaul (MFH) networks that employ both coherent detection (CD) and direct detection (DD) technologies. To optimize application performance and network efficiency, we propose phase-coded three-level pulse amplitude modulation (PAM-3) for multicast traffic delivery to CD and DD nodes. We implement several connectivity scenarios based on both typical and improved PAM-3 in an SDN fronthaul testbed and examine the pre-forward error correction (FEC) bit error rate (BER) performance for 25 Gbaud signals. Using low-density parity-check (LDPC) codes to achieve the desired post-FEC BER levels, we study the performance gains due to code rate adaptation in dynamic wavelength-routing MFH networks.

John Dudley
Real-time measurements of ultrafast instabilities in nonlinear fiber optics: Recent advances
J. M. Dudley¹, P. Ryczkowski², M. Närhi², C. Billet¹, J.-M. Merolla¹, C. Lapre¹, F. Meng¹, P.-A. Lacourt¹, and G. Genty^2
1FEMTO-ST Institute, UMR 6174 CNRS-Université Bourgogne Franche-Comté, Besançon, France
²Photonics Laboratory, Tampere University, Finland
We present an overview of our work in measuring optical instabilities and rogue waves in several scenarios associated with non-linear propagation in optical fibres and laser systems. In recent years, there have been many dramatic advances in the real-time measurement of ultrafast non-repetitive optical signals. Studies carried out have been based on real-time measurements, carried out either in the spectral domain using dispersive Fourier transform techniques or in the time domain using a time lens technique to obtain sub-picosecond resolution. In the context of propagation in nonlinear optical fibres, these real-time techniques have been applied to study modulation instability, supercontinuum generation and optical turbulence. In this presentation, we will review our recent work in this area, and also present the simultaneous use of spectral and temporal techniques to characterize the instabilities observed during the generation of dissipative soliton structures in a fiber laser. These results provide a unique picture of the internal evolution of dissipative solitons in a laser system, and we anticipate further applications of this approach in optimizing laser performance and stability.

Adrian Farrel
A comparative analysis of data models for optical transport networks
A. Farrel and D. King
Old Dog Consulting, UK
The proposal of using Software Defined Networking (SDN) techniques for operating optical transport networks has received a lot of attention. This approach provides centralised planning and control of network resources while collecting status and telemetry from the network to provide feedback and help with planning the delivery of services and optimising the network. A key component of SDN is how the central planning and management components communicate with the network equipment. The current approaches depend on a data model for each device, protocol, or component that is being controlled. These data models are most often written in the YANG language and passed between controller and device using the NETCONF protocol. Over the last several years a number of different standards organisations and open source initiatives have developed distinct modelling approaches for use in optical transport networks. Although the objectives are always the same, the models differ in details and high-level architecture meaning that equipment vendors, network management system developers, and network operators have to make choices or be faced with a complex ecosystem. It would be helpful if the various models and approaches could be consolidated to reduce the options while retaining flexible, high function. This paper makes a comparative analysis of the different data models available with a view to helping decision-makers understand the choices available.

Christophe Finot
Titanium dioxide waveguides for supercontinuum generation and optical transmissions in the near- and mid-infrared
M. Lamy, C. Finot, L. Markey, J. Arocas, J. Fatome, B. Kibler, A. Dereux, J-C. Weeber, and K. Hammani
Laboratoire Interdisciplinaire Carnot de Bourgogne, Université de Bourgogne Franche-Comté, Dijon, France
We report on the development of titanium dioxide waveguides for applications in the near- and mid-infrared. Taking advantage of embedded metal grating couplers, we validate 10 Gbps optical transmissions at 1.55 and 2 µm. With additional management of the dispersion profile, we also demonstrate octave spanning supercontinuum in cm-long TiO2 waveguides.

Fatima Garcia Gunning
Novel real time DC bias monitoring technique for single polarisation quad-drive IQ modulator
N. Canas-Estrada and F. C. Garcia Gunning
Tyndall National Institute, University College Cork, Ireland
Nested Mach-Zehnder modulators, such as DQPSK, DP-mQAm etc., are used in coherent optical communication systems to perform electrical-to-optical data up-conversion and to enable higher order modulation formats in the optical domain. However, their reliability can be affected by drifts in the transfer function, for example due to ambient temperature changes. Maintaining optimum bias voltages (e.g. at quadrature) is a requirement to ensure best performance. We propose a potentially low cost real-time monitoring solution of the biases in nested MZMs using low frequency analogue electronics. This monitoring signal can be used to create an automatic bias control.

Ivan Glesk
On the use of SOA-based tunable dispersion compensator in ultrafast incoherent fiber-optic CDMA systems under temperature variation
Wing C. Kwong¹, S. Seyedzadeh², I. Glesk², and Guu-Chang Yang^3
1Department of Engineering, Hofstra University, Hempstead, USA
²Faculty of Engineering, University of Strathclyde, Glasgow, UK
³Department of Electrical Engineering and Graduate Institute of Communication Engineering, National Chung Hsing University, Taichung, Taiwan
Recently, the use of semiconductor-optical-amplifier-based tunable dispersion compensator (TDC) in ultrafast incoherent fiber-optic code-division multiple-access (FO-CDMA) systems using picosecond multiwavelength codes has been demonstrated. In this paper, the operation principles and experimental results on its capability of fully compensating for fiber chromatic dispersion and distorted auto-correlation peaks caused by temperature variation in a long fiber link are reported. Afterward, the influences of fiber temperature variation to the cross-correlation functions (from interfering codewords) of such FO-CDMA systems with the TDC are studied. Applying the concept of “chip granularity” to quantify the relationship between distorted cross-correlation functions and fiber temperature variation, a new multiple-QoS performance-analytical model for such FO-CDMA systems will be formulated and validated with computer simulation.

Guillaume Huyet
Complex dynamics of long cavity lasers
S. Slepneva^1,2,3, U. Gowda^1,2,3, A. Pimenov⁴, A. G. Vladimirov^4,5, E. Viktorov⁶, and G. Huyet^1
1Université Côte d’Azur, CNRS, INPHINY, France
²Cork Institute of Technology, Cork, Ireland
³Tyndall national Institute, Cork, Ireland
⁴Weierstrass-Institut für Angewandte Analysis und Stochastik, Berlin, Germany
⁵Lobachevsky State University of Nizhny Novgorod, Russia
⁶ITMO University, Saint Petersburg, Russia
The properties of long cw and mode-locked lasers have been the subject of interest as the generators of localised structures and/or for observation of the development of turbulence. Long lasers are also used as highly coherent frequency swept sources for an application in optical imaging and sensing, but the appearance of instabilities limits the coherence length in these devices. Our study aims to analyse the static and quasi-static dynamics of a long laser as it provides an excellent insight on the instabilities experienced in frequency swept sources. We analysed, both experimentally and numerically, the appearance of periodic dark pulses in a long laser and show, that they are closely connected to Nozaki-Bekki holes reported in the complex Ginzburg Landau equation.

Kambiz Jamshidi
A review on the applications and challenges of active silicon ring resonators
K. Jamshidi¹, M. Catuneanu¹, N. Annavarapu¹, S. Dev¹, S. Sabouri¹, R. Hamerly², D. Gray³, C. Rogers³, D. Heydari³, and H. Mabuchi^3
1Integrated Photonic Devices Group, TU Dresden, Germany
²Research Laboratory of Electronics, MIT, USA
³Edward L. Ginzton Laboratory, Stanford University, Stanford, USA
Active silicon waveguides have been used for several applications including parametric conversion and phase regeneration. Compared to other CMOS compatible materials, silicon waveguides have a low threshold for Kerr nonlinearity in Telecom wavelengths. However, in this regime, two-photon absorption results in the generation of carriers. These carriers accumulate and increase the waveguide loss due to free carrier absorption. It has been shown recently that using a ring resonator structure could enhance the phase matching and parameters required for the gain have been analyzed. Furthermore, this structure (with modified parameters like pump power and detuning) can be used for the bistability and free-carrier oscillation. In this paper, a review of these applications and challenges for the realization of the device will be presented.

Tsuyoshi Konishi
Power efficient fine spectral compression for high resolution optical quantization based on intensity-to-lambda conversion
T. Konishi, Y. Kaihori, and Y. Yamasaki
Osaka University, Japan
We experimentally examined how much the power efficient effect of silicon photonics technology can be expected by evaluating the degree of power efficiency for fine spectral compression in optical quantization based on intensity-to-lambda conversion.

Roberto Llorente Sáez
Underwater optical network for remote sensing applications in fluvial environments
V. Vignesh¹, M. Morant², A. Ramirez³, N. Kumar¹, and R. Llorente^4
1Amrita School of Engineering, Bengaluru, India
²Nanophotonics Technology Center, Universitat Politècnica de València, Spain
³Fibernova Systems S.L., Valencia, Spain
⁴Nanophotonics Technology Center, Universitat Politècnica de València, Valencia, Spain
Fluvial environments can be exposed to inadvertent contamination which can degrade water quality. This is of special importance in fluvial environments with streams used for human water supply or agriculture irrigation. Water utilities and public health supervision bodies are concerned by the control of water quality in such environments. However, conventional water quality monitoring methods hinge on laboratory analyses that can take several days. To prevent early water quality degradation, a real-time monitoring infrastructure is required to be deployed on the field. In this paper, a round-the-clock river water quality monitoring system using ad-hoc sensing equipment, an underwater fiber-optic cable and sealed optical interconnections is described. The system consists of a water quality data sensing equipment built to measure and store key fluvial environment parameters such as: water temperature, barometric pressure, pH/ORP, turbidity, RDO and conductivity. In order to functionally validate the proposed system, a calibration process was implemented in the laboratory, and the proper operation was further demonstrated experimentally in a large irrigation channel (Acequia de Pedralba) in the fluvial environment of the Turia River in Valencia, Spain. Successful water quality monitoring in the wide fluvial environment is demonstrated using several probes and over different underwater distances up to 9 km submerged fiber. This prototype system is likely to find extensive utilisation in ecological environments and aquaculture monitoring.

Antonio Napoli
Upgrade capacity scenarios enabled by multi-band optical systems
A. Ferrari, A. Napoli, J. K. Fischer, N. Costa, N. Sambo, E. Pincemin, and V. Curri
Infinera, Munich, Germany
DET, Politecnico di Torino, Italy
Scuola Superiore Sant'Anna, Pisa, Italy
The ITU-G.652D is the most deployed optical fiber, presenting a wide low-loss window with a negligible water absorption peak. Multi-band systems explore this characteristic to extend the transmission capacity. In this work, we show the optical degradation, on the different bands, resulting from successive capacity upgrades (of 80~channels each), till the complete low-loss spectrum is occupied.

Alexandre Pohl
Generation of optical combs based on intensity electro-optic modulators using a differential evolution algorithm
G. F. I. Pendiuk, P. de Tarso Neves Jr., and A. de Almeida Prado Pohl
Federal University of Technology – Parana, Curitiba, Brazil
Generating optical frequency combs using electro-optic modulators is a challenging task as several parameters influence the comb output. In this paper we report on the use of an algorithm based on differential evolution to identify optimal sets of input parameters to modulators used in comb configurations to produce a high number of lines and flatness. Experimental evidence is provided to support the utility of such a technique.

Markus Pollnau
The laser linewidth – Fairy tales and physical evidence
M. Pollnau, Advanced Technology Institute, Department of Electrical and Electronic Engineering, University of Surrey, Guildford, UK
The laser linewidth manifests the spectral coherence of a lasing resonator mode. It is of fundamental importance, theoretically as much as practically. For more than half a century we have been told that the laser linewidth is a result of quantum fluctuations due to spontaneous emission, which induce amplitude and phase fluctuations. Unfortunately, in such a scenario each emission process would violate the law of energy conservation. We show in various ways that a (spontaneous or stimulated) emission process occurs 90 degrees in lead of the incident field, converts one atomic excitation into one photon in the lasing mode and, therefore, conserves the energy, whereas the mentioned fluctuations are the result of vacuum energy and occur at an orders-of-magnitude faster time scale than an emission process. The Schawlow-Townes laser linewidth was originally derived semi-classically and is shown here to be a purely semi-classical phenomenon. We derive the fundamental laser linewidth, which describes transient and continuous-wave, four- and three-level lasers above and below the threshold and show that the Schawlow-Townes linewidth is a four-fold approximation of this linewidth. Also the factor-of-two decrease in linewidth near laser threshold is obtained semi-classically.

Marco Presi
A coherent receiver for analog-over-fiber systems based on feed-forward carrier-recovery
M. Presi, M. Rannello, and E. Ciaramella
Scuola Superiore Sant’Anna University, Pisa, Italy
In this paper, we introduce a Coherent Receiver for Analog-over-Fiber systems. It features a feed-forward phase-recovery scheme: without any digital phase estimation and without employing phase-locked-loops, the system allows RF signals detection with free-running and large linewidth local oscillator lasers. The receiver is presented, and its performance are investigated by means of numerical simulations.

Werner Rosenkranz
Adaptive optical transmission systems employing multidimensional modulation
S. Ohlendorf, T. Wettlin, S. Pachnicke, and W. Rosenkranz
Christian-Albrechts-Universität zu Kiel, Germany
One key aspect of future optical communication systems is the evolution towards link-adaptive systems that offer a high degree of flexibility while keeping the infrastructure unmodified. The spectral efficiency, reach and complexity should be adjustable with a fine granularity by using software updates. The use of multidimensional modulation allows fractional values of bits per symbol in the mapping procedure and therefore enhances the flexibility compared to conventional modulation formats. In this talk, we present a simple and adaptive digital signal processing chain that is suitable for multidimensional modulation in a coherent transmission setup with polarisation multiplexing. The flexibility of the proposed setup is demonstrated in numerical simulations as well as in experimental measurements.

Catalin Stoichita
POF application to building ventilation systems in harsh environment
C. Stoichita, A. Marchewka, and D. Eap
Aereco S.A., France
The modern tall buildings use controlled ventilation systems which are submitted to extreme temperatures, humidity and EM conditions. We describe a system based on POF which breaks few barriers at a time: temperature range, humidity, consumption, reliability and cost.

Weiqiang Sun
Bulk data transfer with store-and-forward in wide area networks
Weiqiang Sun¹, Shengnan Yue¹, Qian Liu¹, Xiao Lin², and Weisheng Hu^1
1State Key Laboratory of Advanced Optical Communications Systems and Networks, Shanghai Institute for Advanced Communication and Data Science, Shanghai Jiao Tong University, China
²College of Physics and Information Engineering, Fuzhou University, Fujian, China
By delaying bulk but delay tolerant data transfers in networks with one or more congested links, the performance and utility of the network can be improved. However, SnF (Store and Forward) imposes significant complexity in the control plane, especially when the network is large and number of requests to be handled is big. This limits its use in real networks. In this paper, we discuss the challenges of SnF of bulk data in WANs, with a particular focus on the control perspective. We summarize our past and ongoing work on this subject and also point out future research directions.

Ioannis Tomkos
Low-cost/power coherent transceivers for intra-datacenter interconnections and 5G fronthaul links
I. Tomkos¹, A. Tolmachev², A. Agmon², M. Meltsin², T. Nikas³, and M. Nazarathy^2
1Athens Information Technology (AIT), Marousi, Greece
²Technion – Israel Institute of Technology, Haifa, Israel
³National Technical University of Athens, Greece
Currently there are certain approaches considered by the optical communications community in order to scale-up the transceiver bit-rates beyond the Tbps mark. They include implementations based on higher baud-rates, advanced modulation formats and some form of parallelism, either by using Parallel Fibers (PSM) or Wavelength Division Multiplexing (WDM), or both. However, the cost and power consumption of the resulting transceivers, normalized per Gb/s, do not drop linearly as the number of parallel lanes (utilizing either spatial or spectral resources) increase. The cost and power consumption targets for the associated transceivers are particularly stringent for the case of intra-datacenters connectivity and 5G fronthaul links, unlike the cases of inter-datacenter connectivity and terrestrial/submarine networks. For intra-datacenter and 5G fronthaul interconnections, it would be ideal to develop solutions that can operate with a single I/O fibre and be based on single-wavelength implementations. Coherent detection, can certainly offer a nice solution in that direction for scaling the transceivers towards higher capacities; however the cost and power consumption issues stemming mainly from the use of ultra-high-speed DSP chips and ADCs (consuming over 8 W, even at 7 nm technology) must be addressed. Therefore Coherent transceivers that avoid the use of DSP chips and DAC-less transmitters have certainly high future potential, despite the fact that at the moment they are inferior to the other existing solutions in terms of transmission performance. However, the performance requirements for intra-datacenter and 5G fronthaul transceivers are not so demanding, as compared to the case of longer-reach transceivers, and as a result some of these simpler transceiver designs can find their path to commercialization for intra-DCI and 5G fronthaul. In our presentation, we will present the different options that have been proposed in the literature for DSP-chip-less coherent transceivers and we will focus on a particular implementation that uses only analogue signal processing.

Stefan Wabnitz
Multidimensional shaping of spatiotemporal waves in multimode nonlinear fibers
S. Wabnitz¹, A. Niang², D. Modotto², A. Barthelemy³, A. Tonello³, V. Couderc³, V. Kermene³, A. Desfarges-Berthelemot³, M. Fabert³, E. Deliancourt³, K. Krupa⁴, and G. Millot^4
1DIET, Sapienza University of Rome, Italy
²University of Brescia, Italy
³University of Limoges, France
⁴University of Bourgogne, France
Recent experiments have shown that nonlinear wave propagation in multimode optical fibers leads to complex spatio-temporal phenomena. In this talk, we introduce new approaches for the control and the optimization of nonlinear beam reshaping in the spatial, temporal and spectral dimensions. The first approach applies spatial beam self-cleaning the technique of transverse wavefront shaping, which permits to launch an optimized input mode combination, that results in the stable generation of a whole nonlinear mode alphabet at the fiber output. The second approach introduces a longitudinal tapering of the core diameter of multimode active and passive fibers, which permits to generate ultra-wideband and high brightness supercontinuum light, featuring high spatial beam quality.

Cédric Ware
Interoperability issues in optical transport networks
L. Alahdab^1,2, C. Ware², E. Le Rouzic¹, J. Meuric¹,and A. Triki^1
1Orange Labs, Lannion, France
²LTCI, Télécom ParisTech, Université Paris-Saclay, Paris, France
To reduce network infrastructure cost, network operators want to integrate interoperable and open transponders, since these transponders allow application of the latest technologies over legacy networks at a competitive price. This process, commonly called "alien wavelength" support, requires that the network management software be able not only to control the new transponders, but also estimate lightpath performance. Avoiding vendor lock-in, standard sets of parameters and protocol extensions enable the use of vendor-agnostic open-source tools.

Changyuan Yu
Application of seven core fiber-based sensor on torsion angle measurement and vital signs monitoring
Changyuan Yu¹, Fengze Tan¹, Zhengyong Liu², Shuyang Chen¹, and Zhenyu Huang^1
1Department of Electronic and Information Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong
²Department of Electrical Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong
Apart from spatial-division multiplexing optical fiber communication system, seven core fiber has been widely investigated for optical fiber sensing application, such as high temperature, strain and vibration sensors. In this work, we further explored the application of seven core fiber on both conventional industry community and popular healthcare area. On one hand, a novel optical fiber torsion sensor was designed using tapered seven core fiber and demonstrated to measure torsion angles with tunable sensitivity. Moreover, the proposed torsion sensor owns the ability to discriminate the rotation direction with stable performance. On the other hand, based on the interference between the center core and surrounding cores in seven core fiber, an optical fiber interferometer was proposed using conventional sandwich structure to monitor the vital signs and activities of patients on bed. Respiration signals can be obtained and on bed/off bed/body movement activities can be recognized using this seven core fiber-based interferometer.

5GT invited presentations:

Young Lee
Extended ACTN architecture to enable end-to-end 5G transport service assurance
Young Lee¹, J. Kaippallimalil¹, and R. Vilalta^2
1Huawei Technologies, Plano, USA
²Centre Tecnològic de Telecomunicacions de Catalunya (CTTC), Castelldefels, Spain
This paper is aimed to provide a novel approach for an end-to-end service assurance mechanism for 5G back-haul transport network. Abstraction and Control of TE Networks (ACTN) in an IETF standard architecture enabling virtual network operations to operate, control and manage large-scale multi-domain, multi-layer and multi-vendor TE networks, so as to facilitate network programmability, automation, efficient resource sharing. This paper extends ACTN architecture as well as 3GPP 5G architecture to address service assurance and performance guarantee for an end-to-end 5G backhaul transport networks.

Paulo Monteiro
Low latency dynamic bandwidth allocation algorithms for NG-PON2 to support 5G fronthaul and data services
A. Zaouga^1,2, A. de Sousa¹, M. Najja², and P. Monteiro^1
1Instituto de Telecomunicações, Departamento de Eletrónica, Telecomunicações e Informática, Universidade de Aveiro, Portugal
²Communication Systems Laboratory (SysCom), National Engineering School of Tunis (ENIT), University of Tunis El Manar (UTM), Tunisia
In this paper, we have proposed Dynamic Bandwidth Allocation (DBA) algorithms for NG-PON2 to support both 5G fronthaul services and data services that achieve a maximum upstream 5G fronthaul delays lower than the delay requirements imposed by 5G fronthaul. The proposed DBA scheme is different from the classical DBA for NG-PON2 in terms of the number and the structure of the allocated time slots. Moreover, we investigated the number of ONUs that can be accommodated by our proposal and the guaranteed throughput to data services in every ONU in addition to the impact of the transmitted packet size on US 5G fronthaul delays.

Raul Muñoz
Experimental validation of network slicing management for vertical applications on multimedia real-time communications over a packet/optical network
P. Alemany¹, R Vilalta¹, J L de la Cruz¹, A Pol², A Román², R Casellas¹, R Martínez¹, and R. Muñoz^1
1Centre Tecnològic de Telecomunicacions de Catalunya (CTTC), Castelldefels, Spain
²Quobis, O Porrino, Spain
This paper presents the network slice manager developed in SONATA NFV Service platform used to partition the 5G network and dynamically deploy network slices with quality of service (QoS). Network slices exist in parallel and isolated for the different tenants (e.g., vertical industries) in order to deliver the tenant-specific requirements (e.g., latency, bandwidth). The network slice manager has been experimentally tested in the multimedia real-time communications pilot deployed in the 5GTANGO project, considering the development and instantiation of two slices with different QoS.

Salvatore Spadaro
Actuation framework for 5G-enabled network slices QoE/QoS guarantees
R. Montero, F. Agraz, A. Pagès, and S. Spadaro
Advanced Broadband Communications Centre (CCABA), Universitat Politècnica de Catalunya, Barcelona, Spain
Network slicing is identified as the enabling technology for efficient service delivery in future 5G networks. Moreover, a key aspect in 5G network slicing relates to the delivery and maintenance of QoS/QoE guarantees of the provisioned slices. The paper discusses an overall framework for triggering the proper actuations to restore the provisioned end-to-end network slices requirements. In particular, a policy-based actuation system is adopted, in which a policy framework creates policies tied to specific behaviors in regards of configurations needed at the whole infrastructure.

Jarosław Turkiewicz
Optical transmission technologies for 5G networks
J. P. Turkiewicz, Institute of Telecommunications, Faculty of Electronics and Information Technology, Warsaw University of Technology, Poland
One of the key challenges in 5G network roll out is realization of the dedicated transmission system and networks able to cope with the traffic demand, while keeping the cost low. The paper presents studies on the cost effective transmission technologies and potential for their application in the 5G networks. Among other 850 nm, 1310 nm and space division multiplexed transmission are addressed and their applicability to the 5G networks is evaluated.

Ricard Vilalta
End-to-end network service deployment over multiple VIMs using a disaggregated transport optical network
R. Vilalta¹, J. L. de la Cruz¹, P. Alemany¹, R. Casellas¹, R. Martínez¹, A. Muqaddas², R. Nejabati², and D. Simeonidou^2
1Centre Tecnològic de Telecomunicacions de Catalunya (CTTC/CERCA), Barcelona, Spain
²University of Bristol, UK
5GTANGO has extended SONATA NFV platform in order to be used to deploy network services over multiple VIMs, which are interconnected. A WAN infrastructure Manager (WIM), developed in the context of 5GPPP METRO-HAUL, is responsible for tackling the necessary connectivity services. In this paper, we propose to use ONF Transport API (T-API) as WIM NBI, with the purpose to control the underlying optical disaggregated network. SONATA NFV platform requests the necessary connectivity through its novel T-API plugin.

ACCESS invited presentations:

José Altabás
Advanced technologies for coherent access networks
J. A. Altabas^1,2, D. Izquierdo^2,3, J. Clemente², S. Sarmiento⁴, G. Silva Valdecasa^1,5, M. Squartecchia¹, L. F. Suhr¹, O. Gallardo¹, A. Lopez², M. Á. Losada², J. Mateo², J. Bevensee Jensen¹, J. A. Lazaro⁴, I. Garces^2
1Bifrost Communications, Scion DTU, Kgs Lyngby, Denmark
²Aragon Institute of Engineering Research, University of Zaragoza, Spain
³Centro Universitario de la Defensa, Academia General Militar, Zaragoza, Spain
⁴Universitat Politècnica de Catalunya, Barcelona, Spain
⁵DTU Elektro, Kongens Lyngby, Denmark
Coherent technologies are exhibiting the flexibility and performance required to address the next generation of optical access networks, where the residential, business and mobile backhaul will converge. The use of these technologies for access networks is done form several approaches, as affordable photonic integrated circuits (PICs) and cost-effective transceivers. An interesting proposal for affordable PICs for optical access network is a 2x3 coherent receiver, which allows a populated wavelength division multiplexing causing an increment of the overall capacity of the network. In addition, the coherent cost-effective transceivers, as the directly-phase modulated VCSELs or the quasi-coherent receivers, will have a relevant role for reducing the overall cost of the network but fulfilling the future requirements. The advanced modulation formats will also contribute to address the requirements of the future optical access networks. They will allow to introduce new concepts as pay-as-you-growth in the optical access network employing the non-orthogonal multiple access (NOMA) combined with carrierless amplitude phase modulation (CAP). They will also allow to use intensity modulated spectrally efficient formats as OFDM, FBMC, UFMC and GFDM.

Pierpaolo Boffi
Disruptive photonic technologies for the future sustainable high-capacity metro network
A. Gatto¹, P. Parolari¹, M. Rapisarda¹, C. Neumeyr², S. Bhat³, G. Delrosso³, M. Svaluto Moreolo⁴, J. M. Fabrega⁴, L. Nadal⁴, P. Boffi^1
1Politecnico di Milano, Dipartimento di Elettronica Informazione e Bioingegneria, PoliCom Lab, Milano, Italy
²Vertilas GmbH, Garching, Germany
³VTT Technical Research Centre of Finland Ltd, Espoo, Helsinki, Finland
⁴Centre Tecnològic de Telecomunicacions de Catalunya (CTTC/CERCA), Castelldefels, Barcelona, Spain
An original technological solution based on the exploitation of long-wavelength VCSELs directly-modulated with multicarrier modulation formats is proposed to implement multi-Tb/s transceivers for the next-generation metropolitan area network. The developed modular approach in the design and realization of the transmitter guarantees scalability and low cost, low power consumption and reduced footprint.

Joseph Kahn
Adaptive coding and modulation for robust 50G PONs
E. Chou and J. M. Kahn
Stanford University, E. L. Ginzton Laboratory, Department of Electrical Engineering, Stanford, USA
Adaptive coding and modulation (ACM) allow passive optical networks (PONs) to trade bit rate for receiver sensitivity on a per-subscriber basis, enabling reliable operation at reduced margin. We propose a 50G PON that transmits at a fixed symbol rate using 2-, 3-, or 4-ary pulse amplitude modulation (PAM). Further rate variation is provided by puncturing or shortening a low-density parity-check code to obtain hard-decision-decoded forward error-correction at rates between 0.6 and 0.9. Other system improvements are considered, including optimized PAM level spacing, avalanche photodiodes, and equalization. The system supports received optical powers spanning 10 dB range at bit rates of 15-50 Gb/s.

Paola Parolari
Effect of filtering in dense WDM metro networks adopting VCSEL-based multi-Tb/s transmitters
P. Parolari¹, A. Gatto¹, M. Rapisarda¹, C. Neumeyr², M. Svaluto Moreolo³, J.M. Fabrega³, L. Nadal³, and P. Boffi^1
1Politecnico di Milano, PoliCom – Dip. Elettronica Informazione e Bioingegneria, Milano, Italy
²Vertilas GmbH, Garching, Germany
³Centre Tecnològic de Telecomunicacions de Catalunya (CTTC/CERCA), Castelldefels, Barcelona, Spain
Long-wavelength vertical cavity surface emitting laser (VCSEL) can represent an alternative solution for the development of transmitters with reduced cost, power consumption and footprint for very-high capacity metropolitan area systems. Multi-Tb/s transmitter modules with fine wavelength division multiplexing (WDM) granularity can be obtained adopting direct modulation (DM) with advanced modulation formats, such as discrete multitone (DMT), and aggregating multiple DM-VCSELs emitting in the C-band with WDM multiplexers in SOI chips. Due to numerous hops between nodes inside metropolitan area networks the effect of filtering can severely impact the transmission performance; we evaluate the transported capacity in function of nodes number and filtering shape, taking into account the actual VCSEL parameters.

Josep Prat
Direct PSK-ASK modulation for coherent udWDM
J. Prat, J. C. Velasquez, and V. Polo
J. Prat, J. C. Velasquez, and J. Tabares
Universitat Politécnica de Catalunya, Barcelona, Spain
By means of pulse shaping, direct laser modulation reveals as an efficient low-cost option for future coherent ultra-dense-WDM-PON access systems, achieving sensitivities below -40 dBm with channel spacings of 6.25 GHz only.

Josep Segarra
Versatile metro-access network integrating FTTH, enterprises, IoT and 5G services
J. Segarra, V. Sales, and J. Prat
Universitat Politècnica de Catalunya, UPC, Barcelona, Spain
Bandwidth demands are increasing with a high dynamic shape, driven by high definition video, cloud-computing, business services, Internet of Things (IoT) and emerging next generation mobile networks like 5G. To support this variable pattern, reconfigurable capabilities are to be delivered to access and metro networks. Furthermore, considering wireless networks, a centralized processing in a Cloud-Radio Access Network (C-RAN) needs reconfigurable abilities to bring benefits to mobile systems with dynamic demands of huge bandwidth between Remote Radio Heads (RRHs) at base stations and Baseband Units (BBUs) at the central office. In this paper, we propose a versatile metro-access network integrating FTTH, enterprises, IoT and 5G services. To achieve a high sensitivity and bandwidth efficiency, we will use coherent transceivers and Ultra Dense Wavelength Division Multiplexing (UDWDM), which has been envisioned for future PONs and metro networks to support the increase of access traffic.

Aleksejs Udalcovs
Towards 25+ Gbps/λ IM-DD PON: NRZ, duobinary, PAM4, and DMT transmission and optical budget comparison
A. Udalcovs¹, Lu Zhang², Anders Djupsjöbacka¹, Shilin Xiao², Jiajia Chen³, Sergei Popov³, and Oskars Ozolins^1,3
1Netoworking and Transmission Laboratory, RISE Research Institute of Sweden AB, Kista, Sweden
²State Key Laboratory of Advanced Optical Communication System and Networks, Shanghai Jiao Tong University, China
³School of Engineering Sciences, KTH Royal Institute of Technology, Stockholm, Sweden
While infrastructure providers are expanding their portfolio to offer a sustainable solution for beyond 10 Gbps in optical access network segment, we compare experimentally several alternatives that may be used in future passive optical networks (PONs) to deliver 25+ Gbps net-rates. As promising candidates, we consider the intensity modulation direct detection (IM-DD) systems employing the following modulation formats: (i) duobinary, (ii) 4-level pulse amplitude modulation (PAM4), and (iii) discrete multitone (DMT), which are all more bandwidth efficient than the non-return-to-zero (NRZ) in current 10G PON solutions. In this paper, we focus on the optical budget after transmission over a 20 km single-mode fiber (SMF) link in C-band and discuss the intrinsic imperfections of optical components that may significantly reduce the received signal quality.
[1] S. Barthomeuf et al.: High optical budget 25Gbit/s PON with PAM4 and optically amplified O band downstream transmission, in Proc. ECOC, Sep. 2018, paper Mo4B.1.
[2] S. Barthomeuf et al.: TDM-PON PAM downstream transmission for 25Gbit/s and beyond, MDPI Photonics, vol. 5, no. 45, pp. 1-9, Nov. 2018.
[3] P. Torres-Ferrera et al.: Experimental demonstration of DSP-assisted electrical duobinary optimization for high speed PON 25+ Gbps using 10 Gbps APD receiver, in Proc. ECOC, Sep. 2018, Mo4B.2.
[4] L. Yi et al.: 100Gb/s/λ IM-DD PON using 20G-class optical devices by machine learning based equalization, in Proc. ECOC, Sep. 2018, invited.
[5] K. Zhang et al.: Performance comparison of DML, EML and MZM in dispersion-unmanaged short reach transmissions with digital signal processing, Optics Express, vol. 26, no. 26, pp. 34288-34304, Nov. 2018.
[6] L. Zhang et al.: Nonlinearity tolerant high-speed DMT transmission with 1.5-µm single-mode VCSEL and multi-core fibers for optical interconnects, IEEE/OSA JLT, early access, 2018
[7] R. Lin et al.: 100 Gbps/λ/core NRZ and EDB IM/DD transmission over multicore fiber for intra-datacenter communication networks, Optics Express, vol. 26, no. 8, pp. 10519-10526, 2018.

Xuelin Yang
Physical-layer OFDM data encryption using chaotic QAM mapping
Xuelin Yang, A. Sultan, A. A. E. Hajomer, and Weisheng Hu
Shanghai Institute for Advanced Communication and Data Science, State Key Laboratory of Advanced Optical Communication Systems and Networks, Shanghai Jiao Tong University, China
We proposed new dynamic random QAM mapping to encrypt the user data in OFDM-PON, in order to improve the physical-layer security during data transmission. Instead of scrambling or permutation of the OFDM symbols, a novel random, dynamic and flexible QAM mapping is demonstrated using hyper digital chaos, resulting in a random-distributed constellation plane. Three encryption schemes are studied using constellation-shifting mapping, dimension-constrained mapping as well as circular QAM mapping. In addition, we have compared these encryption schemes in terms of the transmission and security performances. The secure schemes of dynamic QAM mapping based on digital chaos is expected to realize enhanced secure transmission in future OFDM-PONs.

AFLaser invited presentations:

Sonia Boscolo
Excitation of breather solitons in a mode-locked fibre laser
Junsong Peng, S. Boscolo, Zihan Zhao, and Heping Zeng
Aston Institute of Photonic Technologies, Aston University, Birmingham, UK
We report on the generation and study of breathing dissipative solitons in a mode-locked fibre laser. Breathers exist in the laser cavity under the pump threshold of stationary mode locking. For the first time to our knowledge, breathing soliton molecules are also observed. Numerical simulations of the laser model support our experimental findings.

Reinhard Caspary
Polymer fiber lasers
R. Caspary^1,4, F. Jakobs¹, J. Kielhorn¹, Pen Yiao Ang¹, M. Cehovski¹, M. Beck¹, H.-H. Johannes¹, S. Balendat², J. Neumann², S. Unland², S. Spelthann³, J. Thiem³, A. Ruehl^2,3, D. Ristau^2,3,4, and W. Kowalsky^1,2,4
1TU Braunschweig, Institut für Hochfrequenztechnik, Braunschweig, Germany
²Laser Zentrum Hannover e.V., Hannover, Germany
³Leibniz Universität Hannover, Institut für Quantenoptik, Hannover, Germany
⁴Cluster of Excellence PhoenixD (Photonics, Optics, and Engineering – Innovation Across Disciplines), Hannover, Germany
Polymers doped with laser dyes are promising materials for solid state dye lasers. The development of dye doped polymer optical fibers is presented. Furthermore, experimental results from polymer bulk and fiber lasers based on these optical materials are reported.

Marcin Franczyk
Nanostructured core optical fibres for laser applications
M. Franczyk¹, D. Pysz¹, A. Anuszkiewicz¹, A. Filipkowski¹, K. Stawicki¹, J. Lisowska¹, P. Pucko^1,3, D. Michalik^1,2, T. Stefaniuk^1,2, R. Kasztelanic^1,2, R. Stepien¹, K. Markowski⁴, K. Jędrzejewski⁴, T. Osuch^4,5, and R. Buczynski^1,2
1Institute of Electronic Materials Technology, Glass Department, Warsaw, Poland
²Faculty of Physics, University of Warsaw, Poland
³Faculty of Physics, Warsaw University of Technology, Poland
⁴Department of Electronics and Information Technology, Institute of Electronic Systems, Warsaw University of Technology, Poland
⁵National Institute of Telecommunications, Warsaw, Poland
The development of single mode fibre lasers and amplifiers, due to the wide area of applications, is the topic of great interest. We present nanostructurization, the new method applied within the fibre core to control precisely optical properties of the active fibre. The nanostructured core is composed of two or more kind of glasses with the size of a fraction of the light wavelength. The glass areas are made with glass rods creating the structure, repetitive along the fibre. The refractive index of that kind material can be treated as a compound of refractive indices of each glass area averaged over a certain neighbourhood inside the material. It results in continuous-like refractive index profile according to the design, which can be described with effective medium theory. The nanostructurization opens new opportunities for development of fibres with a core composed of glasses doped with active or photosensitive ions. It allows to control precisely not only the refractive index distribution, but also the active dopants distribution or photosensitivity distribution in the fibre core, providing perspectives for novel optical fibre designs for laser applications. We introduce recent developments of nanostructured core fibres made of ytterbium doped phosphate and silica glass. Active fibres with additional germanium dopants are also reviewed.

Jan Mrázek
Nanocrystalline ceramic phosphors for high-power lasers operating at 2 µm
J. Mrázek, I. Kašík, J. Aubrecht, O. Podrazký, J. Cajzl, and P. Peterka
Institute of Photonics and Electronics of the Czech Academy of Sciences, Prague, Czech Republic
Rare-earth (RE) doped silica glass optical fibers became a hearth of modern fiber-lasers. Such lasers are fully competitive with conventional solid-state lasers because of their high brightness, high quality beam, high conversion efficiency, good thermal management, tunability, compactness, size and even flexibility. However, a low solubility of RE inside a silica matrix and a high phonon energy of silica glass strongly reduce the luminescence efficiency of incorporated RE elements. In this concept the RE-doped ceramic nanoparticles are distributed inside a fiber core. The nanoparticles reduce the phonon energy of the matrix and prevent the clustering of RE. Thus they significantly enhance the luminescence efficiency of incorporated RE.  We present a generic sol-gel synthesis of nanocrystalline (RE_xY_1-x)₂Ti₂O₇ (RE=Eu, Ho, Tm)  ceramic phosphors and thin films with tailored structural and optical properties. The effect of the composition and nanocrystalline structure of prepared nanomaterials on their optical properties have been investigated. The optimized nanocrystals were incorporated into optical fibers and the thermal stability during the fiber drawing was investigated. The prepared fiber was tested as an active medium in a fiber-laser ring set-up operating at 2 µm and the fundamental laser characteristics were evaluated.

Ivan Petryshynets
Surface domain structures optimization of soft magnetic materials via the fibre laser scribing
I. Petryshynets, Division of Metals Systems, Institute of Materials Research, Košice, Slovakia
The grain oriented (GO) steels are iron - 3% silicon alloys developed with a strong also called the Goss – type texture to provide very low core losses and high permeability in the rolling direction. These steels are predominantly employed for the transformers with high efficiency. With an additional surface treatment after the rolling process it is possible to improve the magnetic properties of the core material; especially the core losses. At the same time it is well known that laser radiation influence on domain structure with subsequent decrease of specific power losses. In the present work the influence of pulse and continuous laser treatment technique on the magnetic domains modification with positive impact on the final magnetic properties of grain-oriented electro-technical steel has been investigated. The conventional GO steel with silicon content 3 % wt, taken from industrial line after final heat treatment, was chosen as an experimental material. The laser scribing at pulse and continuous processing conditions was applied on the material surface in order to induce thermal stresses, which influence on the modification of the internal structure of magnetic domains. The final domain structures were optimized in relation to the minimization of magnetic losses of the experimental material and to the optimization of thermal stresses application on the surface. The magneto-optical Kerr effect was employed to obtain a visible contrast between antiparallel domains. The domain structures showed that domain-walls positions did not repeat precisely from cycle to cycle, particularly at high inductions, and that the average domain-wall spacing decreased with increasing density of laser scribing lines. Also, the samples were subjected to magnetic measurements as well as nano-hardness and EBSD analysis of heat affected zone before and after laser processing. Clear improvements in final magnetic characteristics were observed for all the regimes using the power density of the laser beam up to 24 W. A semi quantitative relationship has been found between the domain patterns and the used fibre laser treating method. The magnetic losses of the experimental samples before and after laser processing were tested in AC magnetic field with the frequency 50 Hz and induction of 1.5 T. These measurements in magnetic field demonstrated that core losses of investigated steels treated by a specific set of laser scribing parameters were decreased more than 38%.

Alexei Popov
Parametric resonance and theory of Bragg waveguides
A. Popov, V. Baskakov, and D. Prokopovich
IZMI RAN, Troitsk, Russia
During the last decades, powerful infrared lasers made of ytterbium-doped silica fibers are actively designed and tested. The main restriction upon the radiation power is imposed by the quartz destruction threshold of about 1 MW/cm². Therefore a key design element is the fiber diameter increase, however not violating the single-mode generation regime. One of the methods of energy localization in the optical fiber core consists in quasi-periodic modulation of the refraction index in its cladding due to adding a few layers doped with germanium dioxide. A specially designed structure of circular doped layers assures resonance field attenuation in the fiber cladding, impeding energy leakage from the guide core. This effect, analogous to Bragg reflection in crystal gratings, gives way to creation of high-quality optical fibers with large mode area (P. Roy, S. Février, et al., XLIM Research Institute, Limoges, France; M. Likhachev, S. Semjonov, E. Dianov, Fiber Optics Research Center, Moscow). Mathematically, this is reciprocal to the parametric resonance playing an important role in mechanics, electrical engineering, children’s everyday life (rocking the swings), even in the Initial Creation (the latest phase of the Universe inflation). In addition to the method of small perturbation and the well-studied theory of Mathieu equation, we develop a phase variable approach allowing us to construct explicit solutions to a vast family of differential equations with periodic coefficients, beyond small perturbation approximation. The obtained exact solutions are applied to the optimization of the optical guiding structures.

François Sanchez
Coherence measurement of square-pulses in passively mode-locked fiber laser
M. Kemel, G. Semaan, M. Salhi, and F. Sanchez
Laboratoire de Photonique d’Angers, Université d’Angers, France
Square-pulses in passively mode-locked fiber lasers are generally assumed to be the manifestation of the dissipative soliton resonance (DSR). The DSR is a particular solution of the nonlinear propagation equation which does not suffer from any wave-breaking. As a consequence both the energy and the width of the pulses increase linearly with the pumping power while the peak power remains clamped to a fixed value. Another important characteristics of DSR pulses is that they exhibit square shape with a perfect temporal coherence. In this communication we investigate the coherence of square-pulses in a passively mode-locked double-clad fiber laser. We demonstrate that although almost all the characteristics of DSR pulses are verified (energy and width scaling with pump power, peak power clamping, optical spectrum), the square-pulses are not temporally coherent thus demonstrating that square-pulses are not necessarily DSR pulses.

Jacek Żmojda
Plasmon effect in nanocomposite optical fibers for photonic applications
J. Żmojda¹, M. Kochanowicz¹, P. Miluski¹, A. Baranowska², T. Ragiń², and D. Dorosz^3
1Faculty of Electrical Engineering, Bialystok University of Technology, Poland
²Faculty of Mechanical Engineering, Bialystok University of Technology, Poland
³Faculty of Materials Science and Ceramics, AGH - University of Science and Technology, Krakow, Poland
Nanocomposite optical glasses and fibers give a novel way to manage luminescent properties of lanthanides ions, mainly due to their unique properties, obtained as a result of the interaction of metallic nanoparticles with photons. The most advanced systems are found in the currently used waveguide structures, characterized by sophisticated optical properties and an excellent thermal stability parameter required in modern optical fiber technology. State-of-art is a combination of noble metals properties, i.e. silver (Ag⁺), gold (Au⁺) and technology of rare earth (RE) ions doped glassy materials. Modification of emission properties of glassy materials doped with lanthanide ions, which is obtained by co-doping with nano-sized metal particles, is an innovative research area. One of the reasons of introducing nanoparticles of noble metal to glassy materials is the possibility of increasing the luminescence signal in the visible range by energy transfer between metal nanoparticles and rare earth elements and by enhancement of electric field within rare earth ions that results from the surface plasmon resonance. Studies concerning interaction mechanisms of noble metal nanoparticles on luminescent properties of active glasses are currently the subject of research being carried out by many scientific centers around the world. This will lead to new possibilities in the production of optoelectronic devices, including optical fibers sensors and sources currently being used in medicine, optics and nanophotonics (SERS - Surface-Enhanced Raman Scattering, LSPR - Local Surface Plasmon Resonance sensors). In this paper, an effect of silver and gold ions on luminescent properties of europium ions in antimony-germanate-borate SGB glass fibers is presented. The glass was synthesized by standard melt-quenching technique and glass fiber was drown at the temperature of 580 ℃. In the experiment, the interaction mechanism was investigated in terms of localized SPR in each step of the glass fiber fabrication process. Moreover, we demonstrate that self-assembling of silver nanoparticles on glass fiber surface exist only for fiber co-doped with AgNO₃ ions. The non-conventional bottom-up technique of thin film of Ag nanoparticles was analysed by SEM measurements.

BigNeO invited presentations:

Michał Aibin
Deep learning for cloud resources allocation: Long-short term memory in EONs
M. Aibin, British Columbia Institute of Technology – Faculty of Computing, Burnaby, Canada
In this paper, we apply the Long-Short Term Memory (LSTM) to solve the problem of cloud resource allocation in dynamic, real-time traffic scenarios. We use a framework of Software Defined Elastic Optical Networks in cloud environment with the configuration provided by Amazon Web Services. We then explore the various activation functions to compare the performance of LSTM. By using appropriate configuration of LSTM we can overcome issues of high request blocking and achieve acceptable Service Level Agreement, even for high traffic loads.

Alvaro Bernal
Generation and analysis of service-based traffic flows
A. Bernal, M. Ruiz, and L. Velasco
Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
The rapid availability of new services makes that network operators cannot exhaustively test their impact on the network or anticipate any capacity exhaustion. This situation will be worse with the imminent introduction of the 5G technology and the kind of totally new services that it will support. In this paper, we present CURSA-SQ, a methodology to analyze the network behavior when the specific traffic that would be generated by groups of service consumers is injected. CURSA-SQ includes input traffic flow modelling with second and sub-second granularity based on specific service and consumer behaviors. The methodology allows to accurately study traffic flows at the input and outputs of complex scenarios with multiples queues systems, as well as other metrics such as delays.

Vittorio Curri
Synergetical use of analytical models and machine-learning for data transport abstraction in open optical networks (tutorial)
V. Curri, A. D'Amico, and S. Straullu
Politecnico di Torino, Italy
The key-operation to enabling an effective data transport abstraction in open optical line systems (OLS) is the capability to predict the quality of transmission (QoT), that is given by the generalized signal-to-noise ratio (GSNR), including both the effects of the ASE noise and the nonlinear interference (NLI) accumulation. Among the two impairing effects, the estimation of the ASE noise is the most challenging task, because of the spectrally resolved working point of the erbium-doped fiber amplifiers (EDFA) depending on the spectral load, given the overall gain. While, the computation of the NLI is well addressed by mathematical models based on the knowledge of parameters and spectral load of fiber spans. So, the NLI prediction is mainly impaired by the uncertainties on insertion losses an spectral tilting. An accurate and spectrally resolved GSNR estimation enables to optimize the power control and to reliably and automatically deploy lightpaths with minimum margin, consequently maximizing the transmission capacity. We address the potentialities of machine-learning methods combined with analytical models for the NLI computation to improve the accuracy in the QoT estimation. We also analyze an experimental data-set showing the main uncertainties and addressing the use of machine-learning methods to predict their effect on the QoT estimation.             

Lluís Gifre
Interfaces for monitoring and data analytics systems
L. Gifre¹, M. Ruiz², and L. Velasco^2
1Universidad Autónoma de Madrid (UAM), Spain
²Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
Software defined networks (SDN) represents one of the most relevant innovations in recent years for the telecom industry. Major operators are planning to progressively migrate their transport networks, including optical, to such paradigm to take advantage of the programmability of connectivity services. In SDN, resources are abstracted at the networking level and exposed via a north-bound interface to management systems. On the other hand, Monitoring and Data Analytics (MDA) systems can collect monitoring data and make them accessible to external systems, such as billing platforms, to accurately charge users for the services they consume. In addition, in dynamic scenarios, where resources could be created, modified and removed on demand, MDA systems can also facilitate autonomic networking, and thus coordination between SDN and MDA is strictly required. In this paper, we present two monitoring interfaces for MDA systems: the Monitoring (M)-Control, Orchestration, and Management (COM) interface, an east-west interface that enables MDA systems to gather and synchronize operational and telemetry information from multiple COM modules, e.g., an SDN controller or a cloud resource manager, and issue recommendations to the COM modules as a result of data analysis; and the IO4 interface, a MDA north-bound interface that facilitates exporting monitored data to external systems. Functionality of each interface is described from the conceptual viewpoint and relevant operational workflows are proposed.

Pablo Pavon-Marino
NIW: A Net2Plan-based library for NFV over IP over WDM networks
J. L. Romero-Gázquez¹, M. Garrich¹, F.-J. Moreno-Muro¹, M.-V. Bueno Delgado¹, and P. Pavón Mariño^1,2
1Universidad Politécnica de Cartagena, Spain
²E-lighthouse Networks Solutions, Cartagena, Spain
Telecom operators' networks are undergoing through a major technological breakthrough leveraging on the capabilities of Software-Defined Networking (SDN) and Network Function Virtualization (NFV). NFV permits the deployment of virtualized network functions (VNFs) on commodity hardware appliances which can be combined with SDN flexibility and programmability of the network infrastructure. In this paper, we present the NFV over IP over WDM (NIW) library, an open-source framework for SDN/NFV metropolitan networks, created in the context of the Metro-Haul project. NIW is a library added to the Net2Plan open-source network planning software, specifically to model, provision, design and evaluate SDN/NFV networks. First, the major components and functionalities of NIW are introduced in a tutorial manner. Then, we describe an exemplary algorithm which contains different variations for the VNF instantiation and service-chain deployment procedures while taking into account IP over WDM network resources. Finally, the algorithm is applied on a reference topology so as to illustrate the obtainable results employing NIW.

João Pedro
Exploiting real-time performance awareness for cost-effective restoration in optical transport networks
B. Gangopadhyay and J. Pedro
Coriant Portugal, Amadora, Portugal
Real-time performance awareness is one among the many when it comes to recent trends in optical transport networks. Driving the network towards an optimum operating point compared to end of life (EoL) margin stacked over dimensioned networks are some of the key benefits of such real time performance data. The authors exploit the availability of such real time data, which is fairly static over a shorter time window, to be used for network restoration. This paper does a comparison between two network modes where in (i) restoration path and resources are calculated with offline planned EoL performance data and (ii) restoration path and resources are calculated with real time performance data. As the later one excludes margin stacking for future uncertainties (assumptions on fiber cuts, fiber aging, component variations, component aging, model accuracy limitations), the typically longer restoration paths can exploit higher order modulation formats, in some cases matching those employed in the working paths. It is shown that network operators can thus benefit from reduced restoration resources and a lower total cost of ownership (TCO).

Marc Ruiz
Smart filterless optical networks based on optical spectrum analysis
M. Ruiz¹, A. Sgambelluri², F. Cugini³, and L. Velasco^1
1Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
²Scuola Superiore Sant’Anna, Pisa, Italy
³CNIT, Pisa, Italy
Dynamic network operations can produce power fluctuations of the established connections in filterless optical networks. In addition, the gridless nature of filterless networks make that some (un)intentional effects such as transponders laser drift might disrupt the proper operation of lightpaths. To overcome these issues, we present a monitoring system exploiting data analytics and cost-effective optical spectrum analyzers to achieve smart filterless network operation. Experimental measurements are used to validate the proposed data analytics-based approaches, as well as to find the optimal resolution to achieve maximum performance with minimum cost.

Andrea Sgambelluri
Open source implementation of OpenConfig telemetry-enabled NETCONF agent
A. Sgambelluri¹, A. Giorgetti¹, F. Paolucci¹, P. Castoldi¹, and F. Cugini^2
1Scuola Superiore Sant’Anna, Pisa, Italy
²CNIT, Pisa, Italy
Next generation networks are evolving towards disaggregated schemes, where the structure of the optical nodes presents multiple components to be combined and built into a complete solution (i.e., white-box concept). In such a scenario, operators and service providers are supporting vendor neutrality to enhance devices inter-operability, simplify the control-plane operation and reduce network costs. OpenConfig is a working group of network operators focused on the definition of a set of vendor-neutral data models allowing dynamicity and programmability of the infrastructure by mean of software-defined networking paradigm. Moreover, the telemetry functionality is a new solution for network monitoring in which data is efficiently streamed from devices and continuously. Maintaining an accurate view of key transmission parameters at the controller enables an effective control of the network, with specific impact on the detection of faults (i.e., hard and soft failures) and hardware degradation. In this paper, we propose an open-source implementation of an OpenConfig NETCONF agent enhanced with telemetry service. Other than NETCONF configuration and monitoring functionalities, the adoption of the gRPC-based telemetry allows the on-demand streaming of real-time monitoring parameters from the transponders, enabling the deep analysis of the devices. In fact, the controller is able to request the streaming of one or more selected parameter(s), on demand and with proper granularity, in order to detect and localize the presence of a fault or identify hardware degradation. The implemented telemetry-enabled NETCONF agent for transponders has been experimentally validated over an EON scenario, highlighting the main functionalities and the effectiveness of the proposed solution.

Behnam Shariati
Feature-based optical spectrum monitoring for failure detection and identification
B. Shariati^1,2, M. Ruiz¹, J. Comellas¹, and L. Velasco^1
1Optical Communications Group (GCO), Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
²Fraunhofer Heinrich Hertz Institute HHI, Berlin, Germany
Failure identification and localization can reduce failure repair times greatly. Even though there are available solutions monitoring the performance of lightpaths at the transponder side to verify their proper operation, monitoring the signal at the egress node does not allow localizing failures and therefore, monitoring techniques to analyse and evaluate the QoT in-line are required. In this regard, the availability of cost-effective OSAs, integrateable in the optical nodes, allows real-time monitoring of the optical spectra of the lightpaths. Therefore, optical spectrum features can be exploited by machine learning based algorithms to detect degradations and identify failures. In this paper, we review different approaches to detect filter related failures. The first set of approaches are based on a set of classifiers that make predictions using meaningful features extracted from the optical spectrum. These approaches can deal with filter cascading effects in different ways: i) the multi-classifier approach, in which different classifiers are employed for signals experiencing different levels of filter cascading and ii) the single-classifier approach, in which the lightpaths’ features are pre-processed to compensate for the filter cascading effect allowing the use of a single classifier for lightpaths regardless of the level of filter cascading. The second approach, called residual-based approach, uses the residual signal computed from subtracting the signal acquired by OSAs from an expected signal synthetically generated. Ultimately, the optical spectrum analysis can be used by centralized algorithms able to localize failures in the network. The proposed approaches for failure detection and identification can be deployed in the monitoring and data analytics (MDA) agents, close to the devices generating measurements, whereas other algorithms, including the one for failure localization, need to be deployed in the MDA controller, so as to provide the global network vision required.

Fatemehsadat Tabatabaeimehr
Distributed and centralized options for self-learning
F. Tabatabaeimehr, M. Ruiz, and L. Velasco
Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
In general, the availability of enough real data from real fog computing scenarios to produce accurate Machine Learning (ML) models is rarely ensured since new equipment, techniques, etc., are continuously being deployed in the field. Although an option is to generate data from simulation and lab experiments, such data could not cover the whole features space, which would translate into ML models inaccuracies. In this paper, we propose a self-learning approach to facilitate ML deployment in real scenarios. A dataset for ML training can be initially populated based on the results from simulation and lab experiments and once ML models are generated, ML re-training can be performed after inaccuracies are detected to improve their precision. Illustrative numerical results show the benefits from the proposed self-learning approach for two general use cases of regression and classification.

Alba Vela
Visualization tools for enhancing failure localization
A. P. Vela, M. Ruiz, and L. Velasco
Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
The use of data visualization techniques is explored to guide human operators in failure localization tasks. In this paper, we consider the case where a subset of lightpaths’ experience gradual BER degradation. We aim at using visualization techniques that guide a human operator to find out the most likely resource that is responsible for such degradation, as well as when such degradation started. Note that the challenge is to analyze an amount of data that might be huge (e.g., 1 sample every 15 min for the last, let us say, 4 weeks, for every lightpath in the network) and display charts in seconds, while revealing meaningful information for human operators. The proposed task-oriented visualization tackles such challenge by using charts that first help finding the subset of affected lightpaths thus, reducing the number of lightpaths to be analyzed. In a second step, different charts are used to reduce the element in failure as much as possible. Finally, the few suspicious elements can be analyzed in detail using more traditional timeline graphs. Keywords: data visualization, data analysis, failure localization and optical networks.

Luis Velasco
Monitoring and data analytics for optical networking
L. Velasco and M. Ruiz
Optical Communications Group (GCO), Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
Increased levels of automation will be necessary in view of more stringent performance requirements that next generation optical transport networks need to support in a near term, not only for high capacity, but, even more importantly, for dynamicity, latency, and availability. All these aspects will become more relevant with the growing complexity of modern networks. Network automation targets resource re-optimization to rapidly adapt the network to the expected conditions, quick degradation detection to improve the quality of the connections, as well as failure detection and identification to facilitate maintenance. Network automation requires and implies the collection of data for performance monitoring, being then elaborated by data analytics algorithms to produce meaningful inputs for the network controller, which will finally program the underlying devices. In this paper, we analyze alternative architectures for monitoring and data analytics (MDA) and illustrative control loops are presented aiming at validating the usefulness of MDA to automate optical networks operation.

CTS invited presentations:

Noureddine Boudriga
On the design of an intelligent landing and take-off assistance system using optical wireless communication
D. Krichen, W. Abdallah, and N. Boudriga
Communication Networks and Security Research Lab., University of Carthage, Tunisia
In this paper, we propose an all optical network architecture for a smart landing and take-off assistance application. Our network combines visible light communication (VLC), fibre optics and free space optics (FSO) technologies and is composed of optical sensor nodes that collect information about the state of the runway and relay it to two gateways. The latter will recover the sensed information and transmit it to the approaching aircrafts. In addition, we propose a new sensor node architecture based on low cost and versatile plastic optical fibres to measure the runway condition using intensity detection scheme. In sensor node architecture, one fibre is used to transmit the light, whereas the second fibre collects the light reflected by the target point in the monitored runway. The reflective property of these sensor nodes allows them to be used in non-contact applications. After conversion at the photo-detector, the signal is received by the gateway where it is processed and relayed to the approaching aircraft. Furthermore, we investigate the deployment of the nodes at the airstrip borders and we study wavelength assignment using WDM and graph colouring to reduce interference. Finally, we evaluate the communication performances of the proposed network in terms of transmission delay and bit error rate.

Jaafar Elmirghani
Energy efficient resource allocation in vehicular cloud based architecture
A. A. Alahmadi, M. O. I. Musa, T. E. H. El-Gorashi, and J. M. H. Elmirghani
School of Electronic and Electrical Engineering, University of Leeds, UK
The increasing availability of on-board processing units in vehicles has led to a promising integration between clouds and VANETs under the concept of vehicular clouds (VC), a new form of mobile edge computing (MEC). In this paper we propose an architecture integrating VC with metro network fog nodes and the central cloud located in the core network to ensure service continuity. We tackle the problem of efficient resource allocation in this architecture by developing a Mixed Integer Linear Programming (MILP) model to minimize energy consumption by optimizing the assignment of different tasks to the available resources in this architecture. We study service provisioning considering different assignment strategies and varying application demands and analyze the impact of these strategies on the utilization of the VC resources.

Joan García-Haro
Overview of approaches for detecting the environmental conditions of non-motorized vehicles in urban centres
V. Beltran¹, A. J. Garcia-Sanchez², and J. Garcia-Haro^2
1RobinBrick S.L., Spain
²Department of Information and Communication Technologies, Universidad Politécnica de Cartagena (UPCT), ETSIT, Spain
Private transportation by bicycle or other non-motorized means is increasingly common in urban centers. Not only these modes of transport have clear economic and environmental benefits, but they are also often faster than motorized vehicles due to frequent traffic jams in congested cities. Non-motorized transportation should be as comfortable as possible to promote it further. This article investigates how smartphones carried by drivers of non-motorized vehicles can collect data about the environment and exploit these data to improve drivers' comfortability. A comparative survey on different proposals that take a Vehicle-to-Infrastructure (V2I) communication approach is presented.

Kira Kastell
Cell crossing probability and location-based handover in hybrid mobile networks
K. Kastell, Fachhochschule Frankfurt am Main – University of Applied Sciences, Frankfurt am Main, Germany
In this paper the cell border crossing probability to a certain target cell is predicted by means of location measurement data taken by mobile networks without the aid of a positioning system. This probability is needed for a secure handover in a hybrid network consisting of different radio access networks. Each of the contributing networks has its own security level that should not be weakened by any handover procedure. Therefore authentication has to be included in the handover procedure. Based on the cell crossing probability the handover procedure is redefined finding a trade of between protocol overhead and network security. The amount of overhead heavily depends on the cell size and velocity of the mobile device and cannot be reduced to the theoretical minimum using inbuilt localization, but it can be decreased down to a tolerable value.

Tetsuya Kawanishi
Reconfigurable radio-over-fibre networks for interference mitigation in linear cell radars
T. Kawanishi, T. Miura, and K. Inagaki
National Institute of Information and Communications Technology (NICT), Tokyo, Japan
This paper proposes a novel network configuration for mitigation of interference between radar units in a linear cell radar system. For airport applications, false images would be generated by strong reflection on smooth surfaces of aircraft. Such false images due to interference between any two radar units can be suppressed by switching configuration of optical links which connect the radar units, where group delays in the links depend on the configuration.

Erich Leitgeb
Approach for an optical network design for autonomous vehicles
D. Kraus, H. Ivanov, and E. Leitgeb
Graz University of Technology, Austria
Currently still most of the number of different types of vehicles (cars, aeroplanes, etc.) is increasing. Also the technology of the vehicles is still growing in complexity, improvements and network-ability. For example, Advanced Driver Assistance Systems (ADAS) such as Traffic Sign Recognition, Lane Keeping Assist System (LKAS), Collision Avoidance System, Automatic Parking and even Vehicular Communication Systems are already available in state-of-the-art vehicles. A modern wiring harness, for example, can exceed the weight of several passengers and thus influences the driving behaviour as well as fuel consumption. This setup is often quite expensive, and the complexity increases with every single addition to the network. The number of sensors, actuators, cameras, and other systems is steadily increasing to improve road safety of vehicles. In autonomous scenarios, the amount of systems, and thus the complexity, is significantly higher compared to state-of-the-art vehicles. As a result, the additional weight of components such as computers, control units, and cables directly influences the driving behaviour and fuel consumption. Additionally, all the electronic components must be shielded against electromagnetic interferences to prevent system failures. In this paper, existing bus systems are analysed for their capabilities to handle sophisticated network traffic which will emerge in autonomous vehicles. Furthermore, problems are identified and discussed, and a potential solution based on optical technologies is presented. This solution combines existing optical technologies in a novel way to cope with the upcoming bandwidth requirements of autonomous vehicles, while keeping the costs to a minimum. Regardless of the basic requirements, such as real-time, safety, security and so on, - certain conditions must be met. Otherwise, it is impossible to ensure the functionality of an application, the vehicle, and in a wider sense, the physical integrity of the passengers. Consequently, the goal is to optimize existing systems in terms of weight, cost, safety and functionality.

Alicia López
Statistical approach for modeling connectors in SI-POF avionics systems
A. López¹, A. Losada¹, D. Richards², J. Mateo¹, Xin Jiang², and N. Antoniades^2
1Photonics Technology Group (GTF), Aragón Institute of Engineering Research (i3A), Universidad de Zaragoza, Spain
²Department of Engineering and Environmental Science, College of Staten Island, The City University of New York, USA
The application of POFs as the media in avionics networks requires the introduction of a large number of connections whose loss can greatly reduce the power budget. Moreover, the presence of connectors in POF links also changes the system bandwidth depending on their positions. A methodology for engineering SI-POF and connectors was previously devised by embedding a matrix framework into commercial software and was applied to evaluate the performance of a typical avionics system including a number of connectors. In that study, the connector model was deterministic assuming that the connected fibers were always in the same position and thus, the system average behavior was obtained but its variability was not provided. In avionics platforms, air-gap connectors are preferred to avoid fiber damage by physical contact through the vibrations frequent in transportation networks. These statistically variable positional shifts add to the already large variability present in POF-based systems. Here, our aim is to incorporate connector variability into our simulation methodology to evaluate its impact on transmission properties for an avionics link. Thus, a method based on the calculation of the radiated angular power distribution has been used to upgrade the connector matrix model including lateral and longitudinal misalignments of the input and output fibers. This approach has been applied to perform Monte Carlo simulations of a POF link with several connectors that exhibit longitudinal and lateral offsets drawn from independent statistical distributions. This statistical analysis has been possible by using the Hankel transform in order to speed up the calculations of the high number of samples required to obtain the connector matrices. The use of the SI-POF matrix model combined with the upgraded connector matrix simplifies the testing of different designs and provides not only the mean and standard deviation of power distributions and frequency responses, but also estimates of the probability density functions of parameters such as overall power loss and bandwidth.

Naoaki Yamanaka
Autonomous driving vehicle controlling network using dynamic migrated edge computer function
N. Yamanaka¹, G. Yamamoto¹, S. Okamoto¹, T. Muranaka², and A. Fumagalli^3
1Keio University, Department of Information and Computer Science, Japan
²Alaxala Networks, Japan
³University of Texas Dallas, USA
Autonomous driving vehicle control by edge computer network having very short response time has been proposed. Each vehicle has an agent program on the edge and automatically moved to adjacent edge computer following to the vehicle movement. On the edge computer, agent program is processing with other vehicle agent in the cyber network. We employ triple redundancy and majority rule to achieve high-reliability and less than 10 ms control delay try to be guaranteed. In addition, each vehicle has an IoT sensor including fine-GPS, so all precious position and speed of the vehicle can be monitored. We constricted experimental course, vehicle and edge computer with center cloud and tested in the campus test bed. According to the vehicle movement, network orchestrator setup new optical path automatically and send agent program to the adjacent target edge computer. This orchestration function is newly proposed application triggered dynamic optical network. In this presentation, I will shows the detail experimental results. This architecture and experimental results can be apply to the future smart and connected community.

DACINT invited presentations:

Prince Anandarajah
Tunable active de-multiplexer for optical frequency combs
P. D. Lakshmijayasimha¹, A. Kaszubowska-Anandarajah², P. Landais¹, and P. M. Anandarajah^1
1The School of Electronic Engineering, Dublin City University, Glasnevin, Ireland
²CONNECT Research Centre, Dunlop Oriel House, Trinity College Dublin, Ireland
Optical frequency combs (OFC) sources have recently attracted a lot of interest for their application as multi-carrier transmitters in various high capacity optical communication systems [1] such as data-centre interconnects [2], super channel transmission [3], long-haul networks and many more. OFCs exhibit excellent frequency stability, which enhances the spectral efficiency and could also be used to compensate the Kerr-based nonlinearity, thereby furthering the transmission reach [4]. However, one of the major challenges in the adoption of OFCs, as multi-carrier transmitters in high-speed systems, entails the de-multiplexing of the individual comb tones. Traditional WDM systems have been using the ITU-T standard grid for channel spacing. In such systems, multiplexing and de-multiplexing of the multi-wavelength channels is carried out by arrayed waveguide gratings (AWG), which satisfy the requirements for free spectral ranges (FSRs) of 200, 100, 50 and 25 GHz. However, the next generation communication systems propose FSRs of 12.5 and 6.25 GHz. These denser channel spacing impose a major challenge to the fabrication of optimal filters for the OFC based systems in terms of achieving the stipulated channel isolation. In this paper, the authors demonstrate a tunable de-multiplexer, based on injection-locking technique [5] that can optimally select out tones from a low FSR OFC. Results presented will validate how the proposed method could be used to provide multiple functionality including de-multiplexing, amplification, gain flattening and modulation.
[1] M. Imran et al., A survey of optical carrier generation techniques for terabit capacity elastic optical networks, IEEE Commun. Surv. Tutorials, vol. 20, no. 1, pp. 211-263, 2018.
[2] V. Vujicic et al., Quantum dash mode-locked lasers for data centre applications, IEEE J. Sel. Top. Quantum Electron., vol. 21, no. 6, p. 1101508 (2015).
[3] J. Pfeifle et al., Flexible terabit/s Nyquist-WDM super- channels using a gain-switched comb source, Opt. Express, vol. 23, no. 2, p. 724 (2015)
[4] N. Alic et al., Nonlinearity cancellation in fiber optic links based on frequency referenced carriers, J. Light. Technol., vol. 32, no. 15, pp. 2690-2698, 2014
[5] A. C. Bordonalli et al., Optical injection locking to optical frequency combs for super channel coherent detection, Opt. Express, vol. 23, no. 2, pp. 1547-1557, 2015.

Nikos Bamiedakis
Erbium-doped polymer waveguide amplifiers for board-level optical interconnects
M. Ziarko¹, N. Bamiedakis¹, E. Kumi-Barimah², G. Jose², R. V. Penty¹, and I. H. White^1
1Centre for Photonic Systems, Department of Engineering, University of Cambridge, UK
²Institute for Materials Research, School of Chemical and Process Engineering, University of Leeds, UK
Optical interconnects have an important role to play in next-generation high-performance electronic systems by enabling power-efficient high-speed board-level communication links. Polymer-based optical waveguides is the leading technology for integrating optical links onto standard printed circuit boards as it is sufficiently low cost and enables cost-effective manufacturing and assembly. Various polymer-based optical backplanes have been reported in recent years enabling different on-board interconnection architectures. However, all currently demonstrated systems are purely passive, which limits therefore the reach, complexity and functionality of these on-board systems. Here, we present recent simulation and experimental studies towards the development of Er- doped polymer-based waveguide amplifiers. Two different approaches to integrate Er-doped nanoparticles in siloxane polymer materials are investigated and their potential to yield high-gain waveguide structures is discussed: (i) ultrafast laser plasma implantation and (ii) solution-based dispersion. Simulation results on the achievable performance from such waveguide amplifiers are presented and initial experimental results on waveguide quality and photoluminescence gain from Er-doped polymer thin films and waveguides are reported.

Oskars Ozolins
Multilevel modulation at 100 Gbaud for short reach C-band links
O. Ozolins^1,2, Xiaodan Pang^2,1, A. Udalcovs¹, Lu Zhang², R. Schatz², U. Westergren², G. Jacobsen¹, Jiajia Chen², and S. Popov^2
1RISE Research Institutes of Sweden, Kista, Sweden
²KTH Royal Institute of Technology, Stockholm, Sweden
Datacenters experience an enormous traffic growth due to the vast amount of data to be stored, transmitted and processed [1]-[4]. Technical and economic challenges arise to keep up the bandwidth scalability. Therefore, cost-efficient short reach optical interconnects for 400 GbE intra-datacenter links are critical. Attractive solutions are proposed based on eight optical lanes thanks to compatibility with 100 GbE building blocks, where two optical lanes based 100 GbE solution is already being deployed [4]. Solutions for 400 GbE based on four optical lanes or even two optical lanes using high bandwidth components may be more attractive to reduce cost, power consumption and complexity of parallelism [5], [6]. In this talk, we report on several experimental demonstrations for short reach optical interconnects in C-band. We experimentally evaluate high-speed on-off keying (OOK) and 4-level pulse amplitude modulation (PAM4) and 8-level PAM8 transmitter performance in C-band for short reach optical interconnects. We demonstrate 100 Gbaud PAM4 transmission over 400 meters long standard single mode fiber without optical amplification. We also show results of numerical simulations showing achievable transmission reach in C-band for multilevel modulation at 100 Gbaud over standard single mode fiber with simple decision feedback equalizer. This paves the way for cost-effective short reach optical interconnects with multilevel modulation at 100 Gbaud and higher.
[1] O. Ozolins et al., Short reach optical interconnects with single externally modulated laser operated in C-band, in Proc. ICTON 2018, invited paper We.A3.5.
[2] M. Verplaetse et al., Real-time 100 Gb/s transmission using three-level electrical duobinary modulation for short-reach optical interconnects, J. Lightwave Technol., vol. 35, no. 7, pp. 1313-1319, Apr. 2017.
[3] J. M. Estarán et al., 140/180/204-Gbaud OOK transceiver for inter- and intra-data center connectivity, J. Lightwave Technol., (Early Access) doi: 10.1109/JLT.2018.2876732
[4] X. Pang et al., Experimental study of 1.55-µm EML-based optical IM/DD PAM-4/8 short reach systems, IEEE Photon. Technol. Lett., vol. 29, no. 6, pp. 523-526, Mar. 2017.
[5] O. Ozolins et al., 100 GHz externally modulated laser for optical interconnects, J. Lightwave Technol., vol. 35, no. 6, pp. 1174-1179, Mar. 2017.
[6] O. Ozolins et al., 100 Gbaud 4PAM link for high speed optical interconnects, in Proc. ECOC, Gothenburg, Sweden, Sep. 2017, pp. 1-3.

David Thomson
Silicon optical modulators for data transmission in different wavelength bands
D. J. Thomson¹, Ke Li¹, Wei Cao¹, D. Hagan², Shenghao Liu¹, Fanfan Meng¹, M. Nedeljkovic¹, A. Z Khokhar¹, C. G. Littlejohns¹, Weiwei Zhang¹, M. Ebert¹, A. Shakoor¹, Bigeng Chen¹, Shaif-ul Alam¹, Junjia Wang¹, Xia Chen¹, L. Mastronardi¹, M. Banakar¹, L. Crudgington¹, F. Y. Gardes¹, Jia Xu Brian Sia⁴, Wanjun Wang⁴, Zhongliang Qiao⁴, Xiang Li⁴, Xin Guo⁴, Hong Wang⁴, P. Wilson³, G. Z. Mashanovich¹, A. Knights², and G. T. Reed^1
1Optoelectronics Research Centre, University of Southampton, Southampton, UK
²Department of Engineering Physics, McMaster University, Hamilton, Ontario, Canada
³Department of Electronic and Electrical Engineering, University of Bath, UK
⁴Silicon Technologies Centre of Excellence, Department of electronic and electrical engineering, Nanyang Technological University, Singapore
High-speed and low-power silicon optical modulators are key in realising low cost photonic circuits for data transmission purposes. Depending on the application, different wavelength bands are preferred and therefore designs of optical modulator, which operate in these bands, are required. Here we present our recent work on silicon optical modulators at 1310, 1550, 2000 and 3800 nm wavelengths.

Juan Vegas Olmos
Secure OCDM intra-data center systems enabled by photonic integrated devices
T. R. Raddo¹, J. J. Vegas Olmos², and I. Tafur Monroy^1
1Institute for Photonic Integration, Eindhoven University of Technology, The Netherlands
²Mellanox Technologies, Roskilde, Denmark
Secure communications are perhaps one of the fundamental building blocks in cyber-security efforts against cyber-attacks. Traditionally, security in communications was introduced by means of codification. However, in intra-data center links the usage of codes is considered a necessary evil, since they add latency and increase the power consumption and complexity of the transceivers as they need to incorporate (de)coders. Optical code-division multiple-access (OCDMA) is a physical layer technology natively supporting (de)codification of optical signals on-the-fly; thanks to new advances in photonic integrated circuits (PIC), OCDMA can be effectively introduced in intra-data centers links. In this paper, we introduce the concept of optical encoders and decoders based on PIC technology to implement OCDMA links. Keywords: PIC, encoder, FBG, photonics, optical CDMA

DCN invited presentations:

Nicola Calabretta
SDN-enabled reconfigurable optical data center networks based on nanoseconds WDM photonics integrated switches
Xuwei Xue, K. Prifti, Fu Wang, Fulong Yan, Bitao Pan, Xiaotao Guo, and N. Calabretta
IPI-ECO Research Institute, Eindhoven University of Technology, Eindhoven, The Netherlands
An SDN-controlled optical DCN based on photonics integrated switch enabling QoS-driven network-slice provisioning and reconfiguration is experimentally assessed. Network-slice can be dynamically reconfigured within 150 ms to maintain specified QoS per network-slice. Controlled by the optical flow control protocol, the deployed photonics integrated switches perform error-free 10 Gb/s switching with < 2 dB penalty and zero packet-loss caused by the packet contention.

António Eira
High-capacity metro optical nodes enabling disaggregated edge computing platforms
A. Eira, N. Costa, and J. Pedro
Infinera Portugal, Amadora, Portugal
The convergence of optical metro networks with small data-centers at the edge is reshaping how optical nodes and networks are architected. This paper explores architectures for interconnecting metro optical line systems, transmission hardware and converged switching platforms. For each layer, the suitable service types for the different options are discussed, evaluating both the effect of physical hardware choices, as well as the impact of disaggregation options at a techno-economic and service provisioning level.

Lei Guo
Machine learning-driven virtual network embedding in inter-data centre optical network
Yue Zong¹, Yejun Liu², and Lei Guo^2
1School of Computer Science and Engineering, Northeastern University, China
²School of Communication and Information Engineering, Chongqing University of Posts and Telecommunications, China
The mighty rise of various Artificial Intelligence (AI) applications such as industrial Internet, virtual reality, and driverless transportation incurs massive tasks of data analysis and processing, and thus imposes dramatic burden on the inter-data centre optical network in service provisioning and resource allocation. As one of the enabling techniques in inter-data centre network, Virtual Network Embedding (VNE) is still confined to the conventional resource allocation mechanisms in which the Virtual Networks (VNs) are embedded based on only current traffic profile, while the resource utilization hardly remains constantly optimal due to the time-varying traffic nature. Although VN migration is mostly investigated to address the issue of restrictive resource utilization, the service interruption that frequently occurs during migration is still an intractable obstacle from its practical use. We aim to inject AI into inter-data centre optical network to make sure the constant optimality of network resource utilization. The network traffic is iteratively predicted by collecting the historical traffic data and training the prediction model through machine leaning algorithm. The VN requests are accepted and allocated resource in the aid of not only current traffic profile but also the predicted traffic changes. Through a wide range of simulation tests, we acquire a plenty of insightful results from the traffic prediction model and prove the effectiveness of the proposed VNE algorithm in improving resource utilization and VN acceptance ratio.

Carmen Mas Machuca
Sharing content at the edge of the network using game theoretic centrality
A. Banerjee, N. Sastry, and C. Mas Machuca
Technische Universität München, Germany
Content Delivery Networks aim at delivering to each user, the desired content at minimum delay and cost. In order to tackle this problem, the content placement problem considering available cache locations has been widely studied. However, this paper addresses this problem by taking advantage of using existing and to-date underused Wi-Fi links. Our study considers to cache content in user homes and sharing it among neighbours via Wi-Fi links. To maximise savings, content should be intelligently placed in the edge caches distributed in different users’ homes. We propose using a ‘game theoretic centrality’ metric, which models the sharing of content among neighbours as a co-operative coalition game.

Stephan Pachnicke
Multi-step forecasting of intense traffic streams using machine learning for optical circuit switching
M. Balanici and S. Pachnicke
Christian-Albrechts-University of Kiel, Germany
In this work, we investigate the performance of nonlinear autoregressive neural networks for an efficient prediction of intense data traffic streams for application in hybrid intra-data center networks. The main motivation behind this approach is to evaluate the traffic patterns generated by servers hosting different services and to forecast the occurrence of heavy traffic streams using machine learning. This allows an a priori scheduling and allocation of optical circuit switches for offloading of intense data traffic from electrical packet switches. In this respect, for a realistic analysis, real server generated data gathered over a two-week time span have been used in our simulative evaluation. As with the synthetic data sets used in our previous work, the nonlinear autoregressive neural networks show a promising performance of the forecasting procedure.

Giuseppe Rizzelli
Sensitivity and scaling laws of unamplified coherent architectures for intra-data center links beyond 100 Gb/s
G. Rizzelli and R. Gaudino
Dipartimento di Elettronica e Telecomunicazioni, Politecnico di Torino, Italy
Due to the relentless global data center traffic growth, estimated in 27% annual rate until 2020, many solutions based on coherent detection are being investigated [1] [2] to overcome the limitations of the currently commercially available 100 G technology. Coherent receivers equipped with digital signal processing (DSP) are already well understood and their use in long-haul and metro optical communications is becoming customary [3]. In recent times, several works have proposed the use of coherent detection for short-reach communications in both intra- and inter-data center links, where the main constraints are cost, power consumption and overall complexity. Here, we extend the analytical result presented in [4] to present scaling laws for coherent systems in a data center environment. We evaluate the impact on the coherent receiver sensitivity of system parameters such as power budget, local oscillator power, transmission laser relative intensity noise, transimpedance amplifier noise current, modulation format and bitrate. We then proceed by applying this analysis to several architectures proposed in the literature, such as those originally proposed in [2] and [5].
[1] Xuan He et al., Towards 400Gb/s data center interconnect using coherent detection with higher-order QAM formats, in CLEO, OSA Technical Digest, paper JTu2A.43, (2018).
[2] J. Krause Perin et al., Design of low-power DSP-free coherent receivers for data center links, Journal of Lightwave Technology, 35 (21), 4650-4662 (2017).
[3] A. Schmitt, Tracking the deployment of 3rd generational coherent, Cignal AI Report, www.ciena.com/insights/white-papers, (2019).
[4] Bo Zhang et al., Design of coherent receiver optical front end for unamplified applications, Opt. Express 20, 3225-3234 (2012).
[5] M. Morsy-Osman et al., DSP-free ‘coherent-lite’ transceiver for next generation single wavelength optical intra-datacenter interconnects, Opt. Express 26, 8890-8903 (2018).

ESPC invited presentations:

Toshihiko Baba
Development of non-mechanical beam steering and LiDAR based on photonic crystal and Si photonics
T. Baba, Yokohama National University, Japan
LiDAR is crucial for future robots/drones, ADAS system, autonomous vehicles, etc. Photonic crystal and Si photonics technologies have potential of non-mechanical beam steering and coherent LiDAR. We report the current status of their development.

Walter Belardi
How to amplify light in an unfilled hollow core optical fiber
W. Belardi¹, L. Bigot¹, and P. J. Sazio^2
1Université de Lille, CNRS, UMR 8256 – Physique de Lasers Atomes et Molécules, Lille, France ²Optoelectronics Research Centre, University of Southampton, UK
Optical amplification in a hollow core fiber is typically realised by filling the fiber with a gas and exploiting its active properties. In contrast, here we explore the theoretical possibility of achieving light amplification in an unfilled hollow core antiresonant fiber. In order to do so, we propose and discuss a hollow fiber design based on a combination of resonant and anti-resonant elements within the cladding area.

Ryszard Buczyński
Progress in development of nanostructured gradient index optical fibers and micro-optical components
R. Buczynski^1,2, A. Anuszkiewicz^1,2, A. Filipkowski^1,2, H. T. Nguyen^1,2,3, T. Stefaniuk^1,2, D. Michalik^1,2, M. Franczyk¹, R. Stępień¹, D. Pysz¹, A. Waddie⁴, M. R. Taghizadeh⁴, and R. Kasztelanic^1,2
1Department of Glass, Institute of Electronic Materials Technology, Warsaw, Poland
²Faculty of Physics, University of Warsaw, Poland
³Hong Duc University, Department of Physics, Thanh Hoa, Vietnam
⁴Department of Physics, School of Engineering and Physical Sciences, Heriot-Watt University, Scottish Universities Physics Alliance, Edinburgh, UK
Nanostructured gradient index (nGRIN) elements are a new class of planar-surface micro-optical elements. An effective gradient index profile with any arbitrary refractive index distribution can be developed with internal discrete nanostructure composed of two types of glasses. A low-cost modified stack-and-draw technology commonly used for photonic crystal fibres development is used for development of nGRIN components and fibers. The effective medium Maxwell-Garnett theory is applied to describe performance of the components. We report on recent progress in development of nanostructured core fibres and a wide range of nGRIN micro-optical components as microlenses, axicons, vortices and diffractive optical elements.

Yong Chen
Recent advances in the development of hollow core fibres
Yong Chen, T. D. Bradley, J. R. Hayes, H. Sakr, G. T. Jasion, E. N. Fokoua, I. A. Davidson, S. Rikimi, M. N. Petrovich, F. Poletti, and D. J. Richardson
Optoelectronics Research Centre, University of Southampton, UK
Hollow core fibres (HCFs) has attracted wide attention since it was invented in the late 1990s. Great progress has been made in the last few years in terms of novel designs, loss reduction, and bandwidth increase. In this paper, we review key breakthroughs and main challenges facing in the development of high performance hollow core fibres.

Antonio Díez
Polarization modulation instability in all-normal dispersion microstructured optical fibers with sub-ns pumping
A. Loredo-Trejo¹, Y. López-Diéguez^1,2, L. Velázquez-Ibarra^1,3, A. Díez¹, E. Silvestre⁴, and M. V. Andrés^1
1Departamento de Física Aplicada y Electromagnetismo – ICMUV, Universidad de Valencia, Spain
²División de Ingenierías Campus Irapuato‑Salamanca, Universidad de Guanajuato, México
³Departamento de Física, Universidad de Guanajuato, México
⁴Departamento de Óptica – ICMUV, Universidad de Valencia, Spain
The advent of microstructured optical fiber (MOF) technology gave a significant boost to research in nonlinear optics. MOFs have the advantage of high nonlinearity and designable dispersion, which makes MOFs an excellent platform for efficient generation of nonlinear effects. In the last years, a particular type of MOF exhibiting normal dispersion at any guiding wavelength (ANDi fibers) arised the interest because of the possibility of using them for the generation of coherent and recompressible supercontinuum (SC) light. In this contribution, we will present our recent results regarding the generation of the polarization modulation instability (PMI) effect in ANDi MOFs in the picosecond pump regime at 1064 nm. The experimental observation of this nonlinear effect will be reported, along with the theoretical analysis of it.

Matteo Galli
Demonstration of optical frequency combs in photonic crystal cavities
M. Clementi¹, A. Barone¹, T. Fromherz², D. Gerace¹, and M. Galli^1
1Dipartimento di Fisica, Università degli Studi di Pavia, Italy
²Institute of Semiconductor and Solid State Physics, Johannes Kepler University, Linz, Austria
We report on the design and fabrication of high-Q silicon photonic crystal cavities operating at telecom wavelength exhibiting quasi-equally spaced resonant modes and diffraction limited mode volumes. The cavities design is based on an a bichromatic geometry, resulting in a parabolic profile of the effective confinement potential in analogy with the quantum-mechanical harmonic oscillator. This naturally leads to a nearly equal spacing of the set of resonant modes and Gaussian envelope of the field profile. The fabricated devices exhibit Q factors exceeding one million on multiple modes, as experimentally determined by resonant scattering measurements, and comb-like spectral features. The extremely large field enhancement achievable with these devices, together with the peculiar spectral properties represent a promising platform for scalable integrated nonlinear optical applications based on optical frequency combs.

Frédéric Gérôme
Recent advances on inhibited-coupling guiding hollow-core optical fibers
J. H. Osório, F. Amrani, F. Delahaye, M. Chafer, M. Maurel, C. Restoin, J-M. Blondy, B. Debord, F. Gérôme, and F. Benabid
CNRS-University of Limoges, France
In this talk, we report on recent developments on inhibited-coupling guiding hollow-core optical fibers ranging from the understanding of the guidance mechanism to application fields. We show that a deep understanding of the cladding properties of those fibers allow to obtain fibers with optimized properties. In particular, we demonstrate that, by adequately designing and controlling the fiber physical parameters, one can obtain ultralow loss fibers for the ultraviolet, visible and infrared ranges. Additionally, we show that convenient alterations in the fiber cladding can modify the fiber mode loss hierarchy allowing it to act as a mode shaper, and polarization discriminator.

Romuald Houdré
Optical trapping and gram-type differentiation of living bacteria in 2D hollow photonic crystal cavities
R. Therisod¹, M. Tardif^2,3, N. Villa¹, P. R. Marcoux⁴, E. Picard³, E. Hadji³, D. Peyrade², and R. Houdré^1
1École Polytechnique Fédérale de Lausanne (EPFL), Institut de Physique, Lausanne, Switzerland
²University Grenoble Alpes CNRS,LTM – Micro and Nanotechnologies for Health, Grenoble, France
³University Grenoble Alpes, CEA, INAC, PHELIQS, Laboratoire SINAPS, Grenoble, France
⁴University Grenoble Alpes, CEA, LETI, Minatec-Campus, Grenoble, France
Thanks to their small footprint and to their ability to manipulate objects using low powers, optofluidic systems, based on the integration of photonic structures with microfluidic layers, were shown to be promising tools for biological analysis. Here, we report on the optical trapping and Gram-type differentiation of seven types of living bacteria in 2D hollow photonic crystal cavities. Photonic crystals on silicon and a polydimethylsiloxane (PDMS) frame were respectively processed using standard and soft lithography techniques. A solution of diluted bacteria in de-ionized water was injected in the PDMS frame, letting the bacteria move in unconstrained Brownian motion close to the hollow defect. Excitation of the resonant cavity with a tuneable laser permitted to record multiple trapping events. The analysis of the membrane-dependent resonance frequency shift due to the electromagnetic field-bacteria coupling allowed for the Gram-type differentiation of bacteria in a fast, label-free, and non-destructive way.

Tomasz Stefaniuk
Photonic crystal fibers dedicated to couple, guide and control higher order modes
T. Stefaniuk^1,2, G. Stępniewski², D. Pysz², R. Stępień², and R. Buczyński^1,2
1Faculty of Physics, University of Warsaw, Poland
²Glass Department, Institute of Electronic Materials Technology, Warsaw, Poland
Higher order modes (HOM) in optical fibres exhibit many interesting properties. Among others they have non-Gaussian electric field distributions, complex polarization patterns, unique waveguide dispersion profiles and distinctive propagation characteristics. Therefore, HOMs are used in various types of photonic devices. Here we report on modelling, development and optical characterization of photonic crystal fibers (PCFs) designed especially for the purpose of coupling, guiding and controlling HOMs. In our analysis we concentrate on Mexican sombrero” (HE₁₂) and “doughnut” (HE₂₁, HE₁₁TM₀₁, TE₀₁) modes. We show how to selectively tune their propagation properties and tailor the losses to fit specific applications.

FiWiN5G invited presentations:

Philippe Chanclou
FTTH and 5G xhaul synergies for the present and future
P. Chanclou, L. A. Neto, G. Simon, A. El Ankouri, S. Barthomeuf, and F. Saliou
Orange Labs Network, Lannion, France
This invited paper proposes to discuss the optical network synergies between the two main residential access technologies today: mobile, with the coming 5G, and fixed broadband, which is migrating to full Fiber To the Home (FTTH). 5G aims to offer a fiber-like user experience, providing low latencies and high throughputs. Such requirements impose not only that optical fiber reaches the antenna site (in Fiber To The Antenna topologies, FTTA) but also that optical fibers are used to connect Radio Access Network (RAN) equipment at the antenna site (between Radio Units (RUs) and the cabinet hosting Digital Units (DUs)). At the same time, thanks to FTTH, optical fibers are increasingly more available in the ducts and cabinets for the massive broadband residential deployment. Central offices are equipped with Optical Line Terminal shelves which support Gigabit capable Passive Optical Network (G-PON), 10 Gigabit Point to Point (PtP) and 10 Gigabit symmetrical (XGS-PON) the previous being the coming deployable solution for an enriched fixed broadband. We propose in this paper to investigate the synergies between optical fiber networks (both FTTA for 5G and FTTH), keeping in mind that number of antennas is still very low compared to the number of fixed access premises.

Luca Chiaraviglio
Minimum cost design of 5G networks with UAVs, tree-based optical backhauling, microgeneration and batteries
L. Chiaraviglio^1,2, F. D’Andreagiovanni^3,4, F. Idzikowski⁵, and A. V. Vasilakos^6
1EE Department, University of Rome Tor Vergata, Italy
²Consorzio Nazionale Interuniversitario per le Telecomunicazioni, Italy
³National Center for Scientific Research (CNRS), France
⁴Sorbonne Universites, Universite de Technologie de Compiegne, CNRS, Compiegne, France
⁵Faculty of Electronics and Telecommunications, Poznan University of Technology, Poland
⁶Department of Computer Science, Electrical and Space Engineering, Lulea University of Technology, Sweden
We target the minimum cost design of a 5G network exploiting Small Cells (SCs) carried by Unmanned Aerial Vehicles (UAVs). In our architecture, UAV-SCs can be recharged by a set of ground sites, which provide energy capabilities thanks to the exploitation of micro-generation (i.e., locally produced energy) and batteries. In addition, the ground sites are connected by means of a set of optical fibers forming a tree-based topology. We then define an optimization problem to minimize the total installation costs of the ground sites, the optical network, the batteries, and the sources of micro-generation, while ensuring the coverage of the territory through the UAV-SCs. Results demonstrate that it is possible to notably reduce the total costs compared to a legacy solution, which assumes the installation of fixed Base Stations (BSs) to provide full territory coverage.

Dimitrios Klonidis
5G/NGPON evolution and convergence: The approach of 5G PPP EU project blueSPACE
D. Klonidis and I. Tomkos
Networks and Optical Communications Group, Athens Information Technology (AIT), Marousi, Greece
The EU funded 5GPPP project blueSPACE investigates the use of a SDM/WDM passive optical network architecture that serves as the optical fronthaul infrastructure in 5G. The topology and investigated technologies can support a huge number of remote radio head sites within densely deployed small cells. Here we extend further the considered topology towards hybrid fixed access and wireless fronthaul deployments. This scheme is studied as a viable evolution of NGPON offering convergence potentials with 5G networks.

Nelson Muga
Self-coherent optical detection for access and metro networks
N. J. Muga, R. K. Patel, N. A. Silva, and A. N. Pinto
Instituto de Telecomunicações, Campus de Santiago, Aveiro, Portugal
The 5G-enabled mobile services along with other broadband services will bring unprecedented bandwidth demand on optical networks. In this context, access and optical metropolitan networks will be at the heart of surging demand for high bandwidth and flexibility, and reduced cost per unit bandwidth. This paper presents our recent investigations on new technological paradigms in terms of high-performance and low-cost optical receiver schemes, focusing on self-coherent solutions requiring signal minimum phase condition. We address issues related to the system requirements for the signal reconstruction, in particular, the CW-to-signal power ratio and high-speed digital-signal processing. Keywords: Digital-signal processing, minimum-phase condition, optical detection, self-coherent detection.

Antonio Tartaglia
Optical solutions for 5G: technologies and network architectures
A. Tartaglia, R. Magri, and A. Deho
BNEP DNEP TR Optical Solutions and Fronthaul, Ericsson, Genova, Italy
5G is an huge opportunity for optical technologies to increase their relevance across all networking domains. In this paper we will review how the requirements of 5G are driving new architecture paradigms in networks, and how state-of-the-art optical technologies in the Industry and their evolution can help to meet even the most demanding requirements, keeping the appropriate balance between performance and costs.

Carmen Vázquez Garcia
Power over fiber in radio over fiber systems in 5G scenarios
C. Vázquez, J. D. López-Cardona, D. S. Montero, I. Pérez, P. C. Lallana, and F. M. A. Al-Zubaidi
The Carlos III University, Madrid, Spain
Description: 5G verticals needs of dedicated power architectures for providing efficient systems. Some schematics and measurements on optical power delivery to remote radio heads with 5G scenarios will be described.

Flex-ON invited presentations:

Raul Almeida Jr.
Optical inverse multiplexing technique applied to elastic optical networks
B. V. A. Correia, R. C. Almeida Jr., D. A. R. Chaves, and H. A. Pereira
Federal University of Pernambuco (UFPE), Department of Electronics and Systems, Recife, Brazil
Under dynamic and heterogeneous-bandwidth traffic, the successive establishment and disconnection of call requests may cause the fragmentation problem in elastic optical networks. The fragmentation problem can substantially reduce the network effective spectral usage. One form to mitigate this problem is the use of optical inverse multiplexing (OIM). The OIM technique is based on super-channel multicasting, which allows the network’s call admission controller to relax the continuity and contiguity constraints either by dividing the required spectrum in two or more non-contiguous spectral strips or by performing spectral conversion. This article proposes a novel technique to perform the placement/selection of OIM modules in network nodes. We evaluate the proposal in terms of reduction of blocking probability of call requests and compare it against traditional techniques used in the literature.

Luiz Bonani
On the load normalization in elastic optical networks
L. H. Bonani¹, J. C. F. Queiroz¹, and F. Callegati^2
1Universidade Federal do ABC (UFABC), Santo André, SP, Brazil
²University of Bologna, Cesena, Italy
In recent years, the elastic optical networks (EONs) emerged as a potential technology to support a great variety of bandwidth-consuming applications in core and metropolitan area networks. Within EONs framework, it is possible to choose the modulation formats and/or bandwidth requirements depending on the network available resources and on the required transmission distances. However, it is very difficult to make fair performance comparisons when different topologies and network scenarios with different bandwidth demands and traffic probabilities are considered. In this paper, we present and discuss a new methodology to solve this problem. The strategy is based on the normalization of EONs load and numerical examples are used to illustrate its use and effectiveness.

Daniel Chaves
Review of translucent elastic optical networks under dynamic traffic: Enabling devices, design strategies and operational strategies
H. A. Dinarte¹, B. V. A. Correia¹, R. C. Almeida Jr.¹, H. A. Pereira², and D. A. R. Chaves^3
1Federal University of Pernambuco, Recife, Brazil
²Federal University of Campina Grande, Campina Grande, Paraiba, Brazil
³University of Pernambuco, Recife, Brazil
Regenerators are used in elastic optical networks (EON) to restore the optical signal, as well as, to perform spectrum and modulation format conversions. The EONs that have some regenerators devices in their nodes are also known as translucent networks. Several aspects should be considered during the design of translucent EONs: the type of regenerator employed, the node architecture, the strategies to install and use the regenerators in the nodes. In this paper we review the main approaches proposed in the literature to address the mentioned aspects in translucent EONs under dynamic traffic.

Jaume Comellas
Impact of traffic delay tolerance on elastic optical networks performance
J. Comellas, F. Nourmohammadi, and G. Junyent
Optical Communications Group (GCO), Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
Elastic Optical Networks (EON) are considered as a valuable solution to enhance optical networks efficiency due to their better network resources use. By breaking the traditional fixed grid of WDM networks, spectrum assigned to connection demands is adapted to their requirements. On the other hand, connection parameters such as baud-rate or modulation format are dynamically adjusted taking into account the instantaneous network conditions. In summary, EONs fit perfectly with the heterogeneous characteristics of current and future network traffic loads. Nevertheless, when EONs are in operation, they present some weaknesses mainly derived from the spectrum fragmentation generated by the dynamic establishment and torn-down of these diverse connections. The randomness of connections generation results in the blocking of some connections even when the total load supported by the network is not so high. In this work, we analyse how traffic tolerance to delay impacts on the EON performance, and present simulation obtained results when connection demands have no strict delay constraints compared with demands which need to be real-time served.

Vincenzo Eramo
Proposal and investigation of an optical reconfiguration cost aware policy for resource allocation in network function virtualization infrastructures
V. Eramo¹, T. Catena¹, and F. G. Lavacca^2
1DIET, ”Sapienza” University of Rome, Italy
²Fondazione Ugo Bordoni, Roma, Italy
The paper proposes and investigates the problem of the reconfiguration of cloud and bandwidth resources in Multi-Provider Network Function Virtualization architectures where the Cloud Infrastructures (CI) are managed by different Providers and interconnected by an elastic optical network. The resource reconfiguration is performed by taking into account the different costs charged by the Infrastructure Providers (InP) of the CIs and by exploiting the advantages of the adaptive optical modulation. The objective is to minimize the total cost given by the sum of three components: i) the cloud resource cost; ii) the bandwidth costs; iii) the reconfiguration costs characterized by the revenue loss of the Telecommunication Service Provider due to the degradation of the Quality of Service occurring during the reconfiguration of the optical circuits. We define and investigate a heuristic of polynomial complexity. We show how the heuristic allows for the evaluation of costs very near to the optimal ones. The application of the heuristic to the medium distance Deutsche Telekom network allows for a saving by 40% in total cost with respect to the case in which a traditional policy is applied.

Mirosław Klinkowski
Performance evaluation of multi-core fiber-based dynamic spectrally and spatially flexible optical network with limited transceiver resources
M. Klinkowski¹, G. Zalewski¹, M. Jaworski¹, J. Perello², and S. Spadaro^2
1National Institute of Telecommunications, Warsaw, Poland
²Universitat Politecnica de Catalunya, Barcelona, Spain
We investigate the blocking performance of a dynamic, spectrally and spatially flexible optical network (SS- FON) in which spectral super-channels (SChs) utilizing multiple modulation formats (MFs) are carried over weakly-coupled multi-core fibers (MCFs) and the amount of transceivers (TRX) in network nodes is limited. In the SS-FON scenario considered, lightpath requests may be blocked not only because of the lack of spectrum resources or due to low transmission quality (QoT), as frequently considered in previous works, but also because of insufficient TRX resources. The main goal of this study is to evaluate the joint impact of these three blocking factors on overall network performance.

Yongcheng Li
Rearranging optical amplifiers for upgraded ultra-low loss (ULL) fiber links in an elastic optical network
Yongcheng Li¹, Ningning Guo¹, Wei Chen², Yonghu Yan², and Gangxiang Shen^1
1School of Electronic and Information Engineering, Soochow University, Suzhou, Jiangsu Province, China
²Key Lab. of New Fiber Tech. of Suzhou City, Jiangsu Hengtong Fiber Science and Technology Corporation, China
After the upgrade of new ultra-low loss (ULL) fibers for network links, some optical amplifiers on these links can become redundant. We consider rearranging these amplifiers for a lower system cost while not significantly degrading optical signal transmission performance. In this paper, we consider three amplifier rearrangement strategies and evaluate their performance in terms of the number of amplifiers used and system cost in comparison with the scenario that does not consider the rearrangement.

Uri Mahlab
Traffic load-balancing for software-defined elastic optical networks based cross-entropy technique
U. Mahlab, Y. Wolbrum, and Z. Erlichson
Holon Institute of Technology (HIT), Holon, Israel
The stringent requirements of the 5G to transfer massive data traffic, to various applications, will be based on optimization and utilization of the optical network bandwidth resources. Traffic load balancing management should efficiently optimize the optical bandwidth resources. In this study we present the cross-entropy optimization approach for software-defined elastic optical networks for fiber-load balancing across the network, while meeting the optical and defragmentation constraints, and minimizing the cost of the resulting service disruption, with a reasonable convergence time.

Eiji Oki
Spectrum fragmentation management in elastic optical networks
E. Oki, T. Sato, and B. C. Chatterjee
Communication and Computer Engineering, Graduate School of Informatics, Kyoto University, Japan
In elastic optical networks (EONs), bandwidth fragmentation is a challenging issue, which needs to be suppressed to improve the traffic admissibility. In EONs, lightpaths are established and released dynamically, which cause bandwidth fragmentation that occurs when unoccupied isolated slots are not aligned along the route and contiguous in the spectrum. Bandwidth fragmentation is typically handled by spectrum management approaches. This paper presents recent progress on spectrum fragmentation management in EONs and our latest research activities. The fragmentation management is typically categorized into two approaches, which are non-defragmentation and defragmentation. The non-defragmentation approach avoids spectrum fragmentation when a lightpath is established, and the defragmentation approach rearranges spectrum allocated for established lightpaths in order to repress the effect of fragmentation. Numerical results show that the network performance in terms of traffic admissibility can be improved up to 40% by incorporating spectrum management approaches, when 1% blocking of lightpath requests is considered.

Michela Svaluto Moreolo
Programmable sliceable transceivers based on multicarrier modulation in disaggregated optical metro networks
L. Nadal, J. M. Fàbrega, and M. Svaluto Moreolo
Centre Tecnològic de Telecomunicacions de Catalunya (CTTC/CERCA), Barcelona, Spain
The adoption of open network elements (white boxes), based on different technologies, within the disaggregation network paradigm requires the design/implementation of novel adaptive transceiver architectures. We propose an innovative flexible and programmable multi-rate, multi-format, multi-reach modular sliceable bandwidth variable transceiver (S-BVT) architecture composed of two BVT modules, which can be enabled/disabled according to the network needs. In this talk, the architecture of the programmable sliceable transceiver based on multicarrier modulation (MCM), tailored for optical disaggregated metro networks, is presented. Thanks to the flexibility and cost-effectiveness of the proposed solution, network dynamicity and elasticity can be supported. Additionally, the effect of traversing multiple network nodes based on different technologies is investigated. Special focus is devoted to the activities and recent results achieved within the H2020 METRO-HAUL project.

Krzysztof Walkowiak
Data analytics for improving performance of spectrally-spatially flexible optical networks
K. Walkowiak¹, R. Goścień¹, P. Lechowicz¹, A. Włodarczyk¹, and M. Klinkowski²
1Wroclaw University of Science and Technology, Poland
2National Institute of Telecommunications, Poland
Optimization of lightpath provisioning in spectrally-spatially flexible optical network (SS-FON) is challenging due to many difficult constraints that occur in optical networks and limited amounts of various resources (spectrum, spatial modes, transceivers, regeneration points). Previously demonstrated approaches usually apply fixed provisioning policies (e.g., heuristic routing, space and spectrum assignment (RSSA)) and fail to completely address the characteristic principle and dynamic conditions of SS-FONs. The main objective of this paper is to make a thorough analysis of various data related to performance of SS-FONs in order to identify trends and dependencies that can be next applied to improve optimization of SS-FONs in two aspects: dynamic routing algorithms and static allocation of various resources in the network (transceivers, regeneration points, spatial modes). We present and discuss results of extensive simulations run on two representative network topologies with realistic physical assumptions and under diversified dynamic traffic patterns. As the main performance metric we use bandwidth blocking probability (BBP) assuming 1% threshold of BBP, i.e., we estimate the maximum traffic that can be provisioned in the network with BBP not greater than 1%, which is a commonly acceptably threshold for BBP.

GOC invited presentations:

Taisir El-Gorashi
Energy efficient virtual machine services placement in cloud-fog architecture
H. Alharbi, T. E. H. El-Gorashi, and J. M. H. Elmirghani
School of Electronic and Electrical Engineering, University of Leeds, UK
According to Cisco, in 2017, the total cloud traffic was 75% of all the United Kingdom (UK) Internet traffic. Further growth is projected with expectations that cloud computing traffic will account for 91% of the total traffic in 2022. This proliferation in data volume and processing requests call for a new breed of on-demand computing placement and administration. Fog computing is proposed to reduce the geographic and latency gaps between clouds and users by extending processing and storage resources to the edge of the network. Cloud and fog computing employ virtual machines (VMs) for efficient resource utilization. In order to optimize the virtual environment, VMs can be migrated or replicated over geo-distributed physical machines for load balancing and energy efficiency. In this work, we build a mixed integer linear programming (MILP) model to investigate the offloading of VM services from the cloud to the fog in the British telecom (BT) network. The analysis addresses the impact of different factors including the VM workload, the workload versus number of users profile and the proximity of fog nodes to users considering the data rate of state of the art applications. The result show that the optimum placement of VMs (considering data rates and CPU workloads representing state of the art applications) significantly decreases the total power consumption by up to 74% compared to a single cloud placement.

Gunter Larisch
Reduction of power consumption of optical links based on novel VCSEL optimization strategies
G. Larisch¹ and D. Bimberg^1,2
1”Bimberg Chinese-German Center for Green Photonics” of the Chinese Academy of Sciences at Changchun Institute of Optics, Fine Mechanics, and Physics (CIOMP), China
²Center of Nanophotonics, Institute of Solid State Physics, Technische Universität Berlin, Germany
Thirst for rapidly increasing data rates to satisfy the demands of our internet community leads to an explosion of the energy consumption of data centers. Joint optimization of minimum energy-to-data-ratio EDR and maximum bit rate x distance, damping this trend, seemed to be impossible until now. VCSELs are at the heart of optical links up to distances of  ̴ 1 km. Systematic tuning of their cavity photon lifetime was recently discovered by us to increase the maximum data rate in concert with a reduction of the EDR. Our VCSELs are emitting at 850 nm, 880 nm, 910 nm, and 940 nm, the next IEEE 802.3 wavelength-multiplexing standard for 200+ Gbit/s single fiber data transmission across multimode fiber. Our results for optimized VCSELs across OM5 fiber show, that 50 Gbit/s as bit rate goal in the presently ongoing standardization discussions can be achieved for an EDR = 400 fJ/bit for simple NRZ modulation or alternatively for an EDR much below 100 fJ/bit at 25 Gbit/s. 4 wavelength multiplexing is thus competing with 8 wavelength multiplexing, the latter achieving the same data rates, but for less than 25% of the input power.

Masaya Notomi
Ultrafast and energy-efficient all-optical switching based on graphene-loaded plasmonic waveguides
M. Notomi, NTT Basic Research Laboratories, Department of Physics, Tokyo Institute of Technology, Japan
We have been studying hybrid optical platforms based on a combination of nanomaterials and nanophotonics for pursuing ultimate optical processing. In this talk, we present our recent achievement on graphene-loaded plasmonic waveguides. We combine atomically-thin graphene with deep subwavelength MIM plasmonics waveguides for all-optical switching operation. As a result of the tight light confinement, we have achieved ultrafast and energy-efficient all-optical switching action, showing record-low switching energy at a ps or less time scale.

GOWN invited presentations:

Tibor Berceli
Improvements in radio over fiber links using polarization multiplexing
N. Badraoui and T. Berceli
Budapest University of Technology and Economics, Hungary
The feasibility of 60 GHz radio over fiber (RoF) transmission using polarization multiplexing is paving the way to potential solutions for 5G networks. Polarization multiplexing (Pol-Mux) can be utilized to double the bandwidth efficiency which means to increase the capacity of radio over fiber links. Polarization multiplexing applies two orthogonal polarizations carrying different radio frequency signals in the same optical fiber, simultaneously. We discuss the major transmission impairments of RoF systems applying the Pol-Mux technique. We investigate the transmission problems of these links considering the polarisation mode dispersion (PMD) effects in the case when varying the carrier frequency, fiber length, modulation format, bit rate, etc. We investigate the cross talk effect and its compensation which provides a significant improvement in the link performance. We analyze the quality of the N-QAM signal transmission using numerical simulation in single sideband-based Pol-Mux RoF system.

Vincenzo Petruzzelli
Dielectric and plasmonic Vivaldi antennas for on-chip wireless communication
G. Calò¹, B. Alam¹, G. Bellanca², F. Fuschini³, M. Barbiroli³, V. Tralli², P. Bassi³, T. Stomeo⁴, M. Bozzetti¹, A. E. Kaplan², J. Shafiei Dehkordi², M. Zoli³, J. Nanni³, and V. Petruzzelli^1
1Department of Electrical and Information Engineering, Politecnico di Bari, Italy
²Department of Engineering, University of Ferrara, Italy
³Department of Electrical, Electronic and Information Engineering, University of Bologna, Italy
⁴Istituto Italiano di Tecnologia, Center for Biomolecular Nanotechnologies, Arnesano, Italy
Different technologies enabling wireless on-chip communication are investigated. In particular, plasmonic antennas coupled to silicon waveguides and all-dielectric antennas are proposed also in array configurations to enhance their gain. Moreover, the performances of simple communication links are numerically evaluated.

Christos Verikoukis
SDN/NFV –based network resource management for converged optical-wireless network architectures
M. Mosahebfard¹, J. Vardakas¹, K. Ramantas¹, and C. Verikoukis^2
1Iquadrat Informatica, Barcelona, Spain
²Telecommunications Technological Center of Catalonia (CTTC/CERCA), Barcelona, Spain
This paper proposes a methodology for the efficient allocation of both optical and wireless resources in an SDN/NFV-based converged optical-wireless network architecture. Our approach considers a network slicing architecture where different network slices form end-to-end logically isolated networks, each one dedicated to a different type of service with diverse characteristics. The target of the proposed approach is to optimally determine the network slices so that the specific delay and bandwidth requirements of the multiple services are met, by considering the resources of both the optical and the wireless domains of the network.

LFSRS invited presentations:

Sergey Alexandrov
Label free ultra-sensitive imaging with sub-diffraction spatial resolution
S. Alexandrov¹, N. Das¹, J. McGrath¹, P. Owens², C. J. R. Sheppard³, F. Boccafoschi⁴, C. Giannini⁵, T. Sibillano⁵, H. Subhash⁶, and M. Leahy^1
1School of Physics, National University of Ireland, Galway, Ireland
²Centre for Microscopy & Imaging, National University of Ireland, Galway, Ireland
³Department of Nanophysics, Istituto Italiano di Tecnologia, Genova, Italy
⁴Department of Health Sciences, University of Piemonte Orientale “A. Avogadro”, Novara, Italy
⁵Institute of Crystallography, National Research Council, Bari, Italy
⁶Colgate-Palmolive Global Technology Center, Piscataway, NJ, USA
In this paper, we show a new way to break the resolution limit and dramatically improve sensitivity to structural changes. To realize it we developed a novel label free contrast mechanism, based on the spectral encoding of spatial frequency (SESF) approach. The super-resolution SESF (srSESF) microscopy is based on reconstruction of the axial spatial frequency (period) profiles for each image point and comparison of these profiles to form super-resolution image. As a result, the information content of images is dramatically improved in comparison with conventional microscopy. Numerical simulation and experiments demonstrate significant improvement in sensitivity and resolution.

Vasily Astratov
Resolution enhancement in microspherical nanoscopy by coupling of emission to plasmonics metasurfaces
V. N. Astratov^1,2, F. Abolmaali¹, A. Brettin¹, G. W. Bidney^1,2, Boya Jin¹, N. I. Limberopoulos², D. E. Walker², Hanyang Li³, and A. V. Maslov^4
1Department of Physics and Optical Science, Center for Optoelectronics and Optical Communication, University of North Carolina at Charlotte, USA
²Air Force Research Laboratory, Sensors Directorate, Wright-Patterson AFB, OH, USA
³Key Lab of In-fiber Integrated Optics, Ministry Education of China, Harbin Engineering University, China
⁴Department of Radiophysics, University of Nizhny Novgorod, Russia
The imaging of fluorescent (FL) and non-FL 100 nm nanospheres placed at the top of Al nanoplasmonic arrays is performed through dielectric microspheres with 9-15 µm diameters. The resolution enhancement up to  ̴ λαµβδα/6, where λαµβδα is the emission wavelength, is observed for arrays of nanodisks with sufficiently small (<100 nm) diameters and separations (<20 nm). It is shown that such enhancement is stronger in the case of spectral overlap between the emission band and localized surface plasmon resonance peak in the adjacent plasmonic metasurface. It is hypothesized that the results can be explained by coupling of the emission to the plasmonic “hot spots” followed by the formation of magnified virtual image by the dielectric microspheres with the participation of the resonantly enhanced near-fields.

Shi-Wei Chu
Deep-tissue super-resolution imaging in Drosophila brain
Han-Yuan Lin¹, Li-An Chu^2,3, Hsuan Yang³, Kuo-Jen Hsu^1,2, Yen-Yin Lin², Keng-Hui Lin³, Ann-Shyn Chiang^2,3,5,6,7, and Shi-Wei Chu^1,4
1Department of Physics, National Taiwan University, Taipei, Taiwan
²Brain Research Center, National Tsing Hua University, Hsinchu, Taiwan
³Institute of Physics, Academia Sinica, Taipei, Taiwan
⁴Molecular Imaging Center, National Taiwan University, Taipei, Taiwan
⁵Institute of Systems Neuroscience, National Tsing Hua University, Hsinchu, Taiwan
⁶Institute of Molecular and Genomic Medicine, National Health Research Institutes, Zhunan, Miaoli, Taiwan
⁷Kavli Institute for Brain and Mind, University of California, San Diego, CA, USA
The recent advances of super-resolution microscopy significantly push the frontiers of biology, but the applications to thick tissues are scarce. We described a technique to image an intact brain of Drosophila with 20 nm spatial resolution at 200 mm depth by combining spinning disk confocal microscopy together with molecular localization, blinking fluorescent proteins, and optical clearing. We successfully resolved densely entangled dendritic connectivities, which is crucial for studying whole-brain connectomics, and extendable to larger animals.

Cristiana Grigorescu
Spin plasmonics and surface enhanced Raman spectroscopy in label free biomolecular sensing
C. E. A. Grigorescu¹, A-M. Iordache¹, M. I. Rusu¹, C. R. Stefan (Iordanescu)¹, S. M. Iordache¹, C. Rizea ², T. Soare³, M. Militaru³, A. Diaconescu³, L. Tortet⁴, A. Tonetto⁴, and R. Notonier^4
1National Institute of Research and Development for Optoelectronics INOE 2000, Magurele, Romania
²ROXY VETERINARY S.R.L. Magurele, Romania
³Faculty of Veterinary Medicine-University of Agronomic Sciences and Veterinary Medicine, Bucharest, Romania
⁴Aix-Marseille Universitè, MADIREL & Centrale Marseille, CNRS, Federation Sciences Chimiques Marseille – PRATIM, France
Spin plasmonics emerges as a new field where light can be manipulated through external magnetic fields or magnetic materials. The strong enhancement of electromagnetic fields in spin-plasmonic nanostructures relies on localisation of light at the subwavelength limit. This work is part of a study focused on surface enhanced Raman scattering of biomolecules using magnetic-plasmonic nanostructured substrates. A most desired feature of such future devices is performance at room temperature. The substrates are nanostructured Fe₃O₄ coated with Au and Ag, respectively. Fe3O4 has an inverse spinel structure and a magnetic moment of 4.1µ_B/f.u, a Curie temperature T_C¬850K and is a conductive oxide at room temperature. The Fe₃O₄ nanocompound was prepared via green synthesis. The precursors for Fe(II) and Fe(III) were dispersed in an aqueous solution and were reduced with a phyto-extract. The solution containing nanoparticles of Fe₃O₄ was spin coated onto a stainless steel support and dried (60-200°C) and annealed to 700-750°C. Gold/silver nanocoatings were deposited by dropcast from cyanide free solutions. The effect of the spin-plasmonic structures on the SERS effect is investigated through label free SERS measurements on traces of body fluids and submicron fragments of animal tissue using three laser wavelengths (488 nm, 514 nm, 632 nm) for excitation. The enhancement factor is compared with that resulted from SERS experiments on twin samples deposited on Au and Ag nanostructured surfaces. We foresee applications in histopathology and forensics.

Mikko Huttunen
Investigating human skin using deep learning enhanced multiphoton microscopy
M. J. Huttunen¹, R. Hristu², A. Dumitru³, M. Costache³, and S. G. Stanciu^2
1Photonics Laboratory, Physics Unit, Tampere University, Tampere, Finland
²Center for Microscopy-Microanalysis and Information Processing, University Politehnica of Bucharest, Romania
³Department of Pathology, Carol Davila University of Medicine and Pharmacy, Bucharest, Romania
Histopathological image analysis of stained tissue slides is routinely performed by a pathologist to diagnose diseases, such as cancers. Although the approach is effective, it is labor-intensive, time-consuming and risks being biased. Therefore, it would be beneficial to develop faster and more cost-effective approaches. Multiphoton microscopy can alleviate these problems by allowing label-free imaging with high contrast. When label-free multiphoton microscopy is combined with deep learning based image analysis, a wide variety of possibilities arise for the real-time characterization and diagnosis of tissues. Here, we overview our recent work on this topic focusing on automated classification of tissue images taken from human skin near the dermoepidermal junction.

Konstantinos Iliopoulos
Direct laser writing using chalcogenide thin films
C. Moisset, J-Y. Natoli, A. Bourgade, J. Lumeau, and K. Iliopoulos
Institut Fresnel, Faculté de Sciences de Saint Jérôme, Marseille, France
Direct laser writing has been performed in thin AMTIR-1 layers. By using 10 ns laser pulses, 250 nm thick lines have been written by tightly focusing the laser beam on the thin film layers. The possibility to enhance this resolution by using the Sb₂Te₃ material as super-resolution mask is also discussed.

Femius Koenderink
Shaping light emission by plasmon antenna array lattice resonances with engineered gain and loss
R. Kolkowski and A. F. Koenderink
Center for Nanophotonics, AMOLF, Amsterdam, The Netherlands
Lattice resonances are photonic modes resulting from multiple scattering of light in so-called metasurfaces - dense two-dimensional arrays of polarizable nano-objects. During the past decade, these resonances have been shown to be useful for controlling both spontaneous and stimulated emission of light: especially plasmon nano-antenna arrays have offered improvements in surface-emitting LEDs and lasers in terms of brightness, directivity, and emission efficiency. In our contribution, we will focus on new possibilities that arise when spatially engineering the gain distribution, as opposed to the scatterer geometry. We will present a self-consistent multiple scattering model for metasurfaces with spatially patterned gain. Spatially controlling the gain allows to engineer photonic bands and potentially gives functionalities far beyond simple light amplification. We will in particular focus on structures around points of PT symmetry, and discuss band structures and scattering observables.

Sylvain Lecler
Physics of 3D microsphere assisted microscopy
S. Lecler, S. Perrin, and P. Montgomery
Université de Strasbourg, Télécom Physique Strasbourg, Illkirch, France
In optical microscopy, adding a simple dielectric microsphere near to the sample and below the objective lens has demonstrated the possibility of reaching a Lambda/7 resolution in full field label free 2D imaging. The possibility of measuring the phase and therefore super-resolved 3D profile through such a sphere has also been demonstrated adding a reference arm and using a low coherence source. However, the explanation of this super-resolution is yet not fully understood. The concept of the photonic nanojet, the role of the evanescent waves and of the source coherence will be addressed and confronted with experimental results.

Oleg Minin
Apodization-assisted subdiffraction near-field focusing in 2D phase diffraction grating
I. V. Minin^3,2, Y. E. Geints¹, and O. V. Minin^2,3
1V.E. Zuev Institute of Atmospheric Optics SB RAS, Tomsk, Russia
²National Research Tomsk State University, Russia
³National Research Tomsk Polytechnic University, Russia
Conventional binary phase diffraction gratings can be used to focus optical radiation in the near-field area. By means of numerical simulations, we show for the first time that by engineering a phase diffraction grating with a pupil metal mask the focusing spatial resolution can be substantially improved even beyond the solid immersion limit (λ/2n) accompanied by intensity enhancement. The subdiffraction focusing is due to Fano resonances being excited in the masked binary grating and supported by the anomalous apodization effect. This can be important for advancing the phase grating-based super-resolution technologies, including subdiffraction imaging, interferometry and surface fabrication.

Vahagn Mkhitaryan
2D polaritonics: Fundamental limits and prospects for applications
F. J. García de Abajo and V. Mkhitaryan
ICFO-Institut de Ciencies Fotoniques, Castelldefels (Barcelona), Spain
Two-dimensional polaritons have emerged as powerful tools to manipulate light at atomic scales in materials such as graphene, transition metal dichalcogenides, and atomically-thin metal films. In this talk, we will review recent experimental advances in this front and discuss fundamental properties of these excitations, including their in/out-coupling to light and their potential for applications in sensing, nonlinear optics, and quantum physics.

Evgenii Narimanov
Label-free super-resolution imaging with hyperbolic materials
E. Narimanov, School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, IN, USA
Optical imaging systems based on hyperbolic materials, offer the potential to combine subwavelength resolution with the advantage of an inherently label-free approach. In this talk we review the recent developments in this field, in both direct imaging and structured illumination configurations.

Adrian Podoleanu
Supercontinuum applications in high resolution non-invasive optical imaging
A. Podoleanu¹, O. Bang^2,3, A. Barh³, S. Bojesen⁴, M. Bondu^1,2, A. Bradu¹, S. Caujolle^1,2, C. Chin^1,2, M. Denninger², T. Feuchter², F. Fleischhauer^1,2, M. Hædersdal⁴, G. Hannesschläger⁵, N. Møller Israelsen³, D. Jain³, M. Jensen³, I. B. Gonzalo³, M. Maria^1,2, M. Marques¹, L. Leick², P. Tidemand-Lichtenberg^3,6, M. Mogensen⁴, P. M. Moselund², C. Pedersen^3,6, and C. R. Petersen^3,4
1Applied Optics Group – School of Physical Sciences, University of Kent, Canterbury, UK
²NKT Photonics A/S, Birkerød, Denmark
³Technical University of Denmark, DTU Fotonik, Kgs. Lyngby, Denmark
⁴Department of Dermatology, University of Copenhagen, Denmark
⁴NORBLIS IVS, Virum, Denmark
⁵RECENDT – Research Center for Non-Destructive Testing, Austria
⁶NLIR ApS, Denmark
Progress will be presented in adapting supercontinuum sources to optical coherence tomography. The ultra-wide bandwidth delivered enables sub-micron axial resolution. Several applications of supercontinuum will be discussed as well as the refinement required in signal processing of interferometers driven by a broadband source, that led to the development of complex master slave optical coherence tomography.

Zeev Zalevsky
Label free super-resolved nanoscopy: PALM-like, STED-like and hybrid AFM/NSOM
A. Karsenty¹, A. Chelly², M. Sinvani², H. Pinhas², O. Wagner², Y. Danan², and Z. Zalevsky^2
1Lev Academic Center, Dept. of Applied Physics/Electro-Optics Eng., Advanced Lab. of Electro-Optics (ALEO), Jerusalem, Israel
²Faculty of Engineering and the Nanotechnology Center, Bar Ilan University, Ramat-Gan, Israel
In this presentation we will show three advanced techniques for label-free super-resolved nanoscopy. We will start by presenting a PALM-like concept in which localization precision is converted into spatial imaging resolution. The concept is based upon usage of metallic freely moving nano-particles interacting with the inspected sample. Their temporal-spatial properties of light scattering are used to construct the super-resolved image. This concept is a linear nanoscopy that does not use the non-linearity of fluorescence dye. Then, we will present a STED-like approach in which the non-linearity of plasma dispersion effect of silicon is used in order to generate a sub-wavelength point spread function and to scan with it the inspected silicon wafer. This approach is good for failure analysis of micro-electronic integrated chips or for biomedical imaging if instead of silicon wafers we use silicon freely moving nano-particles. The last concept involves construction of a hybrid atomic force and near field scanning microscope which has an AFM tip into which a photo-detector is integrated and used to perform sub-wavelength photonic sensing instead of the fiber like tip of the conventional NSOM device.

MALOC invited presentations:

Michał Aibin
Machine learning for regenerator placement based on the features of the optical network
S. Cheng, D. Xiao, A. Huang, and M. Aibin
British Columbia Institute of Technology – Faculty of Computing, Burnaby, Canada
With network traffic projected to increase drastically over the new few years, Elastic Optical Networks (EONs) have been brought in to be the successor of the currently used optical technologies. Many factors must be taken into consideration when deploying EONs for wide-scale use. One of which is the overall network's resource allocation. A simple, uniform distribution of regenerators is too inefficient as different locations have different regenerator requirements based on the amount of network traffic they receive. On the other hand, increasing the number of installed regenerators after initial deployment will incur a substantial cost. The ideal scenario is to accurately predict the number of regenerators that each location will need. One way to provide accurate predictions for regenerator allocation is through the use of machine learning. In order to maximize the accuracy of the prediction provided by the machine learning algorithm, it must be supplied with quality input training data. In this paper, we examine the impact that different network features can have on prediction results. We then propose a list of network features that hold significant impact in regards to predicting regenerator allocation accurately.

Abdelkerim Amari
Machine learning-based detection for fiber nonlinearity mitigation
A. Amari, Technical University Eindhoven, the Netherlands
Machine learning techniques have recently received significant attention as promising approaches to deal with the optical channel impairments, and in particular, the nonlinear effects.  Machine learning techniques have been applied as detectors at the receiver side, and also as channel model-based compensation algorithms. They can partially mitigate both deterministic fiber nonlinearities and stochastic nonlinear signal-amplified spontaneous emission noise interactions. In this work, a machine learning-based classification technique, known as the Parzen window (PW) classifier, is proposed  to mitigate the nonlinear effects in the optical channel. The PW classifier is applied as a detector at the receiver side, and the main idea is to design improved nonlinear decision boundaries, more adapted to the nonlinear fiber channel. Performance improvement is observed when applying the PW classifier in the context of dispersion managed and short reach dispersion unmanaged systems.

Danish Rafique
Machine learning based laser failure mode detection
K. Abdelli^1,2, D. Rafique¹, and S. Pachnicke^2
1ADVA Optical Networking SE, Munich/Martinsried, Germany
²Christian-Albrechts-Universität zu Kiel, Kiel, Germany
In this paper we aim employ network fault management techniques to proactively detect laser degradation modes using advanced machine learning algorithms including artificial neural networks, random forest, among others.

Marc Ruiz
Autonomic content delivery network service
L. Velasco¹, L. Gifre², and M. Ruiz^1
1Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
²Universidad Autónoma de Madrid (UAM), Madrid, Spain
The need to provision 5G services within complex end-to-end scenarios, spanning multiple knowledge domains, technologies and administrative boundaries, while doing so dynamically and in a cost-effective way, has driven the design and refinement of functional and protocol architectures and frameworks for the operation of such telecommunication networks and infrastructures. A common trend is to design such service and resource orchestration systems by adopting, extending and building on top of frameworks that follow Software Defined Networking (SDN) and Network Function Virtualization (NFV) principles. Nevertheless, true autonomic operation is achieved if and only if SDN control and NFV management is augmented with instantaneous data-driven decision-making. The use of advanced monitoring concepts and machine learning (ML) tools enable local control loops allowing re-configuration to adapt resources to changing conditions. In this paper, we focus on a use case where a virtualized Content Delivery Network (CDN) service autonomously adapts to the load by requesting the instantiation of new VMs in selected leaf cache nodes, as well as by incrementing the capacity of the network connecting users with the caches. Autonomous decisions are supported by the use of data analytics techniques on monitoring data. Experimental validation supports the feasibility of the proposed autonomic CDN service.

Mariia Sorokina
Neuromorphic processing in optical communications
M. Sorokina, Aston Institute of Photonic Technologies, Aston University, Birmingham, UK
Neuromorphic computing has been recently demonstrated as a lucrative technology for communications systems. Optical neuromorphic technology enables implementation of machine learning algorithms in optical domain. We will discuss the recent progress, as well as, advantages and challenges of such technology for high speed and energy efficient signal processing.

Alba Vela
Autonomous operations in optical networks
A. P. Vela, M. Ruiz, and L. Velasco
Universitat Politècnica de Catalunya, Barcelona, Spain
Machine Learning (ML) has already proven its benefits for network operation, being a sub-domain of artificial intelligence, it is highly suitable for complex system representation. In this paper, basic ML concepts are reviewed, as well as its integration into existing network control and management planes. Then, a use case focused on soft-failure detection is presented in detail covering optical spectrum analysis and ML algorithms; the technique relies on the widespread deployment of cost-effective optical spectrum analyzer (OSA). Finally, the retrieved optical parameters are analyzed using ML algorithms giving rise to illustrative results.

MARS invited presentations:

Germán Arévalo
Optimal dimensioning of the 5G optical fronthaulings for providing ultra-high bit rates in small-cell and femto-cell deployments
G. V. Arévalo¹ and R. Gaudino^2
1Department of Telecommunications Engineering, Universidad Politécnica Salesiana, Quito, Ecuador
²Politecnico di Torino, Italy
In this work we employ the Optimal Topology Search (OTS) algorithm in order to perform an accurate techno-economic analysis of the optimal deployment of 5G networks in large urban areas based on two significant variables: the size of the cells, sweeping sizes from small-cells up to femto-cells, and the bit rate per user, considering bit rates ranging from high up to ultra-high bandwidth access. Results show that the femto-cell solution is the best option for providing ultra-high bit rate access to the users.

João Pedro
Multi-layer optimization framework for optical transport networks with dynamic margin management
J. Pedro^1,2, D. Moniz^1,2, and J. Pires^2
1Infinera Unipessoal Lda, Carnaxide, Portugal
²Instituto de Telecomunicações, Instituto Superior Técnico, Lisboa, Portugal
Optical transport networks are benefiting from the availability of high-capacity and flexible line interfaces, universal optical transport network (OTN) switches, software-defined networking (SDN) controllers and real-time performance monitoring. Individually, each of these building blocks contributes to design and operate transport networks such that cost-effectiveness and robustness are improved. By leveraging their combined capabilities, there is room for further enhancements. For instance, it is envisioned it will enable to adopt an optical channel provisioning strategy that relies on reduced performance margins, increasing the available capacity per optical channel and potentially reducing capital expenditures (CapEx). This paper investigates this premise, describing a transport network architecture and a multi-layer optimization framework tailored for this scenario. Network simulations obtained over two reference transport network topologies highlight that it enables to decrease the number of line interfaces and rerouting events.

Ronald Romero Reyes
Impact of vendor selection on the total cost of ownership of intra-data centre networks
R. Romero-Reyes, V. Vijayakumar Pai, S. Sultana, and T. Bauschert
Technische Universität Chemnitz, Germany
In this paper we study the impact of vendor selection on the total cost of ownership (TCO) of intra-data centre networks. Besides the unit costs of network components, vendors differ in key technical factors that have direct influence on the network TCO. We quantify this influence by evaluating the TCO of selected network architectures when four vendor solutions are considered, namely, Juniper, Cisco, HPE and Brocade. The results show that the vendor solutions mainly differ in the equipment energy consumption and in the ability to upgrade the network capacity as the server port speeds increase. In particular, a sensitivity analysis shows that the changes in the power consumption caused by the traffic load have an impact on the TCO that strongly depends on the vendor selection.

Ken-ichi Sato
How optical-circuit/electrical-packet hybrid switching will create high performance and cost-effective data center networks
Ken-ichi Sato, Nagoya University, Japan
The presentation discusses how to maximize the inherent benefits of optical circuit switching, which matches and makes the best use of advances in silicon switch chips. It is demonstrated that the parallelism of optical switches yields sufficient throughput performance even with simplified and decentralized control that does not need any throughput maximization algorithm. The power consumption of the resulting network is shown to be about 70% less than the electrical alternative. Significant reductions are also verified in the number of fiber links and transceivers. Finally, our recent advances in optical switches based on silicon photonics technologies are presented.

Guang Wu
Severe cold weather is valuable to build Northeast China as the largest data and computing centre in China and in the world
Shaomin Yan and Guang Wu
National Engineering Research Centre for Non-food Biorefinery, Guangxi Academy of Sciences, Nanning, China
Revitalization of economy in Northeast China is very important for sustainable development in Chinese economy because the economy in Northeast China lags behind most parts of China. An important factor, which impedes the economic development in Northeast China, is its severe cold weather. Consequently, the Northeast China faces a series of issues, for example, less attraction to youth, decline of population, aging of population, lack of investment, out-of-date infrastructure, etc. In this study, we propose to restructure the economy in Northeast China from the labour-intensive heavy industry to the high-tech industry based on data storage and computing. This is possible because the severe cold weather is good for cooling data storage and computing facility, which is highly energy-demanded. Taking this economic advantage, it could transform the Northeast China into the largest data storage and computing centre in China, which would promote the development of green economy in China, and even in the world.

MOON invited presentations:

Aymeric Arnould
Ultra-wideband transmission systems based on semiconductor optical amplifiers
A. Arnould¹, J. Renaudier¹, A. Ghazisaeidi¹, D. Le Gac¹, P. Brindel¹, M. Makhsiyan², F. Blache², and M. Achouche^2
1Nokia Bell Labs Paris-Saclay, Nozay, France
²III-V Lab, a joint laboratory between Nokia, Thalès and CEA-LETI, Palaiseau, France
Extending the bandwidth of optical amplifiers is a promising approach to increase the throughput of wavelength division multiplexed (WDM) systems. We review recent ultra-wideband (UWB) experiments and discuss the interest of using UWB semiconductor optical amplifiers (SOA) for future transmission systems. We report on UWB SOA characteristics and discuss recent results of a 300 km transmission experiment over standard single mode fiber (SSMF), using a hybrid Raman and SOA repeater.

Alessio Ferrari
Upgrade capacity scenarios enabled by multi-band optical systems
A. Ferrari¹, A. Napoli², J. K. Fischer³, N. Costa⁴, J. Pedro⁴, N. Sambo⁵, E. Pincemin⁶, B. Sommerkohrn-Krombholz², and V. Curri^1
1Politecnico di Torino, Italy
²Infinera, Munich, Germany
³Fraunhofer Institute for Telecommunications Heinrich-Hertz-Institute, Berlin, Germany
⁴Infinera, Carnaxide, Portugal
⁵Scuola Superiore Sant’Anna, Pisa, Italy
⁶Orange Labs, Lannion, France
The ITU-G.652D is the most deployed optical fiber worldwide and presents a wide low-loss window with negligible water absorption peak. Multi-band systems exploit this characteristic to increase the transmission capacity. In this work, we show the optical degradation in terms of generalized signal-to-noise ratio, on different bands, resulting from successive channel upgrades until the complete low-loss window is occupied.

Daniel Semrau
Overview and comparison of nonlinear interference modelling approaches in ultra-wideband optical transmission systems
D. Semrau, R. I. Killey, and P. Bayvel
Optical Networks Group, Department of Electronic and Electrical Engineering, University College London (UCL), UK
The recent advances in modelling nonlinear interference of systems operating beyond the C-band are discussed. Estimation accuracy as well as computational complexity of current approaches are compared and addressed. Keywords: optical fibre communication, ultra-wideband transmission, nonlinear interference, inter-channel stimulated Raman scattering.

Ioannis Tomkos
Enabling technologies to extend the bandwidth of WDM optical communication systems to the limits of the available optical fiber bandwidth
I. Tomkos, A. Bogris, C. Roeloffzen, A. Liense, A. Larsson, D. Klonidis, N. Raptis, and D. Syvridis
Athens Information Technology (AIT), Marousi, Greece
The increasing demands for high data rate connectivity in access, metro and particularly in core networks dictate the need to increase substantially the capacity of optical networks over the next decade. Significant research work has been carried out, intensively over the last years, towards two main research directions: a) the adoption of spectrally efficient multiplexing schemes, in combination with multi-level signal formats which exploit all parameters of light (e.g. wavelengths, polarization, quadrature), and b) the development of new multi-mode and multi-core fibre transmission systems that enable spatial-division multiplexing (SDM). Both approaches consider an operating bandwidth located mainly in C-band, or slightly extended to S- and L-band (systems with up to 100 nm bandwidth have been proposed as feasible commercial solutions in the past). On the other hand, the widely installed standard single mode fibre has effectively an operating bandwidth in excess of 300 nm, which largely remains underutilized. This is merely attributed to the current technology limitations in both optical amplification and wavelength channel generation and switching.  This presentation intends to present the recent technology advancements in optical communication components (based on wavelength-transparent Silicon Nitride based integrated components) and fiber transmission system solutions that could enable the use of the unutilized fibre bandwidth. We will address the needed advancements that are required in the optical network elements, including both the transmission (e.g. transceiver arrays, amplifiers, multiplexers/de-multiplexers) and node elements (e.g. ROADMs) and will discuss some possible solutions for their implementation.

Emanuele Virgillito
Observing and modeling wideband generation of non-linear interference
E. Virgillito, A. D'Amico, A. Ferrari, and V. Curri
DET, Politecnico di Torino, Italy
Optical line systems (OLS) are going beyond the C-band by exploiting multiple-band transmission to expand the fiber capacity without installing new fiber cables. Moreover, operators are progressively pushing towards the implementation of the open optical network paradigm. This requires the capability to quickly estimate the Quality-of-Transmission (QoT) of  lightpaths  given  by  the  generalized  signal-to-noise  ratio  (GSNR),  including  both  the effects of ASE noise and nonlinear interference (NLI) accumulation. In order to predict the effect  of  NLI  on  GSNR  degradation  of  multiple-band  OLS,  we  first  observe  that  the  NLI generation  can  be  spectrally  disaggregated,  by  separating  the  single-channel  –  self-phase modulation (SPM) – from the multi-channel effects – cross-phase modulation (XPM). Then, relying on the Gaussian-Noise model hypotheses, we derive a mathematical model to assess the  multi-channel effects impairment, validated  by  accurate  split-step  simulations.  We  show  that  the model conservatively predicts the disaggregated NLI intensity generated by the multi-channel nonlinear propagation with an excellent accuracy.

MWP invited presentations:

Mario Armenise
Microphotonics-based architectures of mini-SAR payloads
M. N. Armenise, F. Dell’Olio, C. Ciminelli, C. Galeone, and G. Brunetti
Polytechnic University of Bari, Italy
Photonics is a well-established enabling technology in several technological fields, such as telecommunications, aerospace and defense, life science and health care. In particular, Photonics for Space is becoming a strategic R&D sector for the global aerospace market. The main benefits of photonics over the competing technologies are electromagnetic interference immunity, low power consumption, small footprint, high immunity to vibration/shock and radiation. These requirements are critical on board of satellites and this is the reason why the research effort on photonic sub-systems to be included in satellites for Earth observation (EO) and telecommunications is quickly growing. Synthetic Aperture Radar (SAR) payloads are unanimously considered a very powerful tool for the EO because they exhibit a very good spatial resolution (of the order of 1 m) and can operate in all weather conditions, both during day and night. Typically, SAR payloads have size, mass, and power consumption that make necessity to integrate them on board of a satellite having a mass of the order of a few tons. The current interest towards small satellites (mass in the range 100-500 kg) especially for EO missions demands the development of mini-SAR payload with a mass of some tens of Kg and an average power consumption of the order of 100 W. Thus, several mini-SAR payloads, based on standard electronic components, are currently on the market or under development in some research labs. Aiming at improving the performance of the currently available mini-SAR payloads, several functionalities of the payload, e.g. the generation of chirped waveform that radar transmits, the beamforming, and the direct (without down‐conversion) A/D conversion of the radar echo, can be implemented by integrated microphotonics. In this presentation, we will critically review the state-of-the-art of mini-SAR payloads and discuss how some building block of the system can be implemented in the photonic domain.

Erwin Bente
Radio-frequency signal generation using actively frequency stabilised monolithically integrated InP-based lasers
S. Andreou, K. Williams, and E. Bente
We demonstrate the generation of radio-frequency (RF) signals using stabilized integrated semiconductor lasers. The lasers are monolithically integrated on the same chip using InP active-passive integration technology. They are locked to different resonances of the same external optical cavity using the Pound-Drever-Hall locking technique. The locking is implement with single control loop for each laser and by voltage controlled tuning thus avoiding significant thermal effects. The generated RF signal can be tuned discretely to frequencies that are multiples of the external optical cavity free spectral range. Examples of beat tones at 12.436, 24.8735 and 40.4194 GHz are demonstrated. The linewidth of the generated signals at all frequencies is less than 40 kHz. The single-side-band phase noise is about -54 dBc/Hz for frequencies offsets from the carrier at 12.436 GHz between 1 kHz and 10 kHz and -60 and -67 dBc/Hz at 100 kHz and 1 MHz respectively. Keywords: InP, integration, linewidth, radio-frequency, laser stabilization.

Caterina Ciminelli
Integrated microphotonic switching matrices for flexible and broadband telecom satellite payloads
C. Ciminelli, F. Dell’Olio, G. Brunetti, A. Di Benedetto, and M. N. Armenise
Polytechnic University of Bari, Italy
High-capacity flexible digital payloads for broadband multi-beam missions are strongly demanded by the space industry. The multi-beam approach implies the division of the satellite coverage area into hundreds of cells, each served by a narrow spot beam having a bandwidth typically ≤1 GHz. In a multi-beam telecom payload, each beam is filtered, amplified, down-converted, digitalized, and then processed on-board in the digital domain. After processing, each beam is D/A converted, up-converted, and amplified before retransmission. Several functionalities within such payloads can be implemented in the photonic domain with a consequent performance enhancement. In particular, switching is a core function for all telecom payloads and its implementation by integrated microphotonics or MOEMS (Micro-Opto-Electro-Mechanical System) technology is under investigation since at least 15 years. Although MOEMS switching matrices intended for space applications have been experimentally studied, a critical aspect of this technology, i.e. the scalability, still remains. Integrated microphotonic switching matrices based on ring resonators, which have been widely investigated for terrestrial applications, could be a valid alternative to the MOEMS approach. In this presentation, the state-of-the-art of the photonic switching matrices is critically reviewed and those technological solutions that seem more appropriate for the use in flexible and broadband telecom payloads are discussed.

Ivana Gasulla
Few-mode fiber true time delay lines
S. Garcia, R. Guillem, and I. Gasulla
ITEAM Research Institute, Universitat Politecnica de Valencia, Spain
Space-division multiplexing optical fibers cannot only provide parallel channel transmission but also parallel distributed signal processing, being this a feature particularly attractive in Microwave Photonics applications. We present here few-mode fiber links with tailored modal propagation and dispersion properties that operate as sampled true time delay lines for radiofrequency signals.

Paolo Ghelfi
Distributed coherent radars enabled by fiber networks
P. Ghelfi¹, L. Lembo^1,2, F. Scotti¹, G. Serafino³, S. Maresca³, and A. Bogoni^1,3
1PNTLab, CNIT, Italy
²CSSN Naval research Center, Italian Navy, Italy
³TeCIP Institute, Scuola Superiore Sant’Anna, Italy
In the last few years, we have been proposing the use of photonics to bring new functionalities in radar systems, exploiting its precision and tunability to give radars improved performance and reconfigurability. The talk will present the most recent evolution of the original idea of photonics-based radars, which considers the exploitation of the increasingly available fiber connections to implement a network of widely distributed radars. The centralized photonic approach allows driving several separated radars simultaneously, enabling the novel class of distributed coherent radar systems. Through the implementation of specific multi-input multi-output (MIMO) processing, the photonics-enabled radar network is capable to push the detection resolution far beyond the limits usually set by the radar signal bandwidth.

Marco Grande
Reconfigurable and optically transparent graphene-based devices
M. Grande^1,2, G. V. Bianco², F. Kashif¹, M. Scalora³, G. Bruno², and A. D’Orazio^1
1Dipartimento di Ingegneria Elettrica e dell’Informazione, Politecnico di Bari, Italy
²Istituto di Nanotecnologia – CNR-NANOTEC, Bari, Italy
³Charles M. Bowden Research Center, RDECOM, Redstone Arsenal, AL, USA
The quest for reconfigurable and optically transparent devices in photonic and microwave applications is increasing over the last years. This growing research interest is driven by the opportunity to combine photonic and microwave technologies, thus creating unprecedented tools. In this framework, graphene can be a game-changer due to the ability to modify and tune its electromagnetic behavior in both photonic and microwave ranges. In this paper, we will review the latest achievements in graphene-based reconfigurable devices and will discuss the possibility for new perspectives. Then we will report on the design and characterization of reconfigurable microwave devices such as tunable absorbers and ring resonators that exploit both highly conductive and lossy-dielectric CVD graphene layers [1-2].
[1] M. Grande, G. V. Bianco, et al., Optics Express, 24, 22788-22795 (2016).
[2] M. Grande, G. V. Bianco, et al., Nanotechnology, 29(32), 325201 (2018).

Robinson Guzman
Compact millimeter-wave wireless link using photonic-based broadband transmitter and Schottky-based envelope detector
R. Guzman, M. Ali, A. Zarzuelo, J. Cesar Cuello, and G. Carpintero
Universidad Carlos III de Madrid, Spain
In this paper we report a millimetre (mmWave) wireless link using a photonic-based compact broadband transmitter and a Schottky-based envelope detector, operating within the E-band frequency range. The carrier frequency is generated by optical heterodyne technique, using an 10-GHz bandwidth optical modulator to introduce data at two different data rates (1.5 and 3 Gbps), demonstrating that error-free data transmission (BER < 10^-12) can be achieved. This is a key feature for real time data transmission of ultra-high definition video signals.

Stavros Iezekiel
Microwave photonic linear frequency networks
G. Charalambous and S. Iezekiel
University of Cyprus, Nicosia, Cyprus
We present the concept of microwave photonic linear frequency networks, in which a transfer function for the instantaneous frequency of band-limited microwave systems may be defined and synthesized with microwave photonic components. A self-adaptive bandpass filter is used to illustrate the concept. Such a system is able to track and lock onto the instantaneous frequency of an incoming signal.

Robert Minasian
Advances in microwave photonic beamforming for phased-array antennas
R. A. Minasian and Xiaoke Yi
School of Electrical and Information Engineering, University of Sydney, Australia
Advances in microwave photonic phase shifters for beamforming in phased-array antennas are presented. This includes a grating based microwave photonic phase shifter structure, which features a simple configuration only requiring a single control to shift the RF signal phase, and which can be extended to obtain multiple phase shifts. It demonstrates a continuous phase shift capability with low amplitude variation and low phase deviation over a wideband microwave range. Also, an integrated silicon photonics on-chip phase shifter based on single all-pass micro-ring resonator is described. This is based optical single sideband modulation in conjunction with control of the separation between the laser wavelength and the resonance wavelength of the micro-ring to change the phase of the RF signal after photodetection. Experimental results have demonstrated a phase shifter with continuous phase tunability at microwave frequencies from 20 to 40 GHz. These microwave photonic phase shifters provide new capabilities for the realisation of high-performance phased arrays.

Carmo Medeiros
Optically generated millimeter wave reflectometry signals approaches followed in the RETIOT project
M. C. R. Medeiros¹, P. Almeida¹, P. Laurêncio¹, and P. M. Monteiro^2
1IT-Instituto de Telecomunicações – Pólo de Coimbra, Departamento de Engenharia Eletrotécnica e de Computadores, Universidade de Coimbra, Portugal
²IT-Instituto de Telecomunicações, Departamento de Eletrónica, Telecomunicações e Informática, Universidade de Aveiro, Portugal
Microwave photonics technologies have been applied successfully to implement reflectometry transceivers operating at millimeter wave frequencies (mmWave) frequencies with very high range resolution. This paper discusses some mmWave generation approaches followed in the project RETIOT (Reflectometry Technologies to Enhance the Future Internet of Things and Cyber-Physical Systems).

Diego Perez-Galacho
Analog radio over fiber links for future 5G radio access networks
D. Perez-Galacho, D. Sartiano, and S. Sales
ITEAM Research Institute, Universitat Politècnica de València, Spain
Bandwidth constraint in the radio access networks is, nowadays, a mayor problem in the implementation of next generation 5G mobile communications. In order to cope with increasing bandwidth demands, the use of the millimeter-wave (mmWave) spectrum, together with Radio over Fiber (RoF) technology has been proposed. In this work, we will present our recent advances in the generation of mmWave signals for 5G using Microwave Photonics.

Salvador Sales
On the use of microwave photonics techniques for novel sensing applications
D. Sartiano, J. Hervás, J. Madrigal, D. Pérez-Galacho, and S. Sales
ITEAM Research Institute, Universitat Politècnica de València, Spain
The potentials of the Microwave Photonics techniques have not been fully exploited yet by the fiber optic sensors research community. We aim to provide the use of MWP concepts for sensing under unknown schemes that can facilitate novel results under coherence regime.

Yevhen Yashchyshyn
New opportunities in quasi-optical materials characterization in far infrared region
Y. Yashchyshyn and K. Godziszewski
Institute of Radioelectronics and Multimedia Technology, Warsaw University of Technology, Poland
Fourier-transform infrared (FTIR) and Time-Domain (TDS) spectroscopies are widely used for material characterization of materials in far infrared region. The main disadvantage of them is limited measurement dynamics especially in lower frequency range. They also require using very thin samples in case of lossy materials. New generation of vector network analyzers (VNA), which are very well known in microwave band, allow measurements in frequency domain up to 1.5 THz with very high dynamics above90 dB. Moreover, the amplitude and the phase of signals can be measured at 32001 frequency points with 1 Hz resolution. These advantages create new opportunities in frequency domain characterization of different types of materials, both lossless and lossy. In this paper a new broadband measurement technique suitable for far infrared range is presented. What is interesting this method does not require any information about thickness of samples under test. Therefore, the electromagnetic properties of different materials (e.g. gases, solid and liquid materials) can be obtained.

Kyriakos Zoiros
SOA-MZI all-optical RoF signal mixing
D. Kastritsis^1,2, K. E. Zoiros¹, T. Rampone², and A. Sharaiha^2
1Democritus University of Thrace, Department of Electrical and Computer Engineering, Lightwave Communications Research Group, Xanthi, Greece
²École Nationale d’Ingenieurs de Brest (ENIB), Lab-STICC (UMR CNRS 6285), Brest, France
Fiber-optic transmission of high radiofrequency (RF) signals is being established as a key means for efficiently dealing with the ever-demanding bandwidth, services and cost requirements of modern broadband wireless networks and systems. Implementation of this technology critically relies on the capability of processing RF signals in the optical layer. A Mach-Zehnder Interferometer (MZI) which incorporates semiconductor optical amplifiers (SOAs) is an attractive scheme for executing all-optically the important task of RF signal frequency transposition via mixing function. In this paper we present the progress and main outcomes obtained so far on the work carried-out to achieve this goal under collaborative project ‘Choraal’. In this context we characterize, evaluate, demonstrate and discuss the performance capabilities, limitations and perspectives of the SOA-MZI when it is architecturally configured to realize RF signal up- and down-conversion into the microwave frequency band. Two different architectures, based on a SOA-MZI acting as an all-optical switch or as an all-optical modulator, are compared.

NAON invited presentations:

Hovik Baghdasaryan
Double-barrier resonant tunneling in nano-optics and quantum mechanics: Wavelength-scale analysis by the method of single expression
H. V. Baghdasaryan¹, T. M. Knyazyan¹, T. T. Hovhannisyan¹, and M. Marciniak^2
1National Polytechnic University of Armenia, Yerevan, Armenia
²National Institute of Telecommunications, Warsaw, Poland
Electromagnetic wave resonant transmission through double thin layers of negative permittivity (double-barriers) separated by a wavelength-scale distance L is analysed. The distances L of resonant transmission are integer numbers of about a half wavelength that corresponding to the well-known conditions of the Fabry-Perot resonator. The distributions of electric field and the Poynting vector along the whole micro-structure at the resonant transmission permit to go deeper in to the physics of the resonant tunneling phenomenon.  In quantum mechanics particle’s resonant transmission through double-barriers separated by the distances L_q are integer numbers of about a half de Broglie wavelength is analysed. The distributions of the probability function and probability flow within the whole double-barrier quantum structure at the resonant transmission permit to go deeper in to the physics of quantum resonant tunneling.  Performed numerical analysis by the method of single expression (MSE) revealed an analogy and a good interfacing of quantum mechanics with nano-optics. 

Gerardo Castañón
Chirp analysis of low-power CMOS nanophotonic modulators
G. A. Castañón, Tecnológico de Monterrey, Mexico
Complementary metal-oxide semiconductor (CMOS) provides an infrastructure for the implementation of a range of integrated photonic modulators, devices and circuits that have the potential to replace the state-of-the-art commercial optical modulators in long-haul communications. An important property of modulators when amplitude modulation is used is their chirp because it affects the effective transmission distance in long-haul optical fiber systems. In this paper we analyze, by the use of simulation, the chirp of CMOS microring modulators operating in the three possible coupling regions named over-coupled, hybrid-coupled, and under-coupled. We used a method that measures the small-signal frequency response of a light emitter, a modulator, a dispersive medium and a light receiver. To quantify the chirp for the large-signal modulation we used the on/off α-parameter calculation, the method is easy, quick, and accurate in calculating the chirp parameter. The numerical results at a wavelength of 1545.3 nm indicate an effective chirp parameter in the range of -2.2 to -0.4 when the ring is over-coupled, when the ring is hybrid-coupled the chirp is 0.63, and when the ring is under-coupled the chirp is in the range of 1.2 to 2. Keywords: Chirp analysis, CMOS photonics, nanophotonic devices, optical communication system.

Maciej Dems
Optimization of semiconductor Bragg mirrors with genetic algorithms
M. Dems, P. Wnuk, P. Wasylczyk, Ł. Zinkiewicz, A. Wójcik-Jedlińska, K. Regiński, K. Hejduk, and A. Jasik
Institute of Physics, Lodz University of Technology, Poland
We present application of a genetic algorithm for optimization of dispersive properties of Bragg reflectors used in femtosecond lasers. The aim of the optimization is designing a mirror with broadband, large negative group delay dispersion (GDD). We were able to achieve GDD of –3500 fs² over a 10 nm bandwidth. We have manufactured the optimized structures with molecular beam epitaxy and verified its performance in a passively mode-locked Yb:KYW laser.

Norbert Hanik
Numerical phase matching optimization for multimode silicon nano-rib waveguides
T. Kernetzky and N. Hanik
The Institute for Communications Engineering, Technical University of Munich, Germany
We optimize four-wave mixing in a multi-mode nano-rib photonic waveguide, in order to achieve broadband all-optical wavelength conversion and optical phase conjugation. For the purpose of maximizing phase matching, we optimize waveguide dimensions, mode-to-laser assignment and pump laser wavelengths. Four-wave mixing efficiency is evaluated with an integral metric and parameters are derived for full C-band operation of optical phase conjugation and wavelength conversion.

Nikolay Ledentsov
Development of 850nm and 910nm vertical-cavity surface-emitting lasers for 50-100Gb/s applications
N. N. Ledentsov¹, V. A. Shchukin¹, V. P. Kalosha¹,  N. N. Ledentsov Jr.^1,2, J.-R. Kropp¹, G. Schaefer¹, Ł. Chorchos², and J. P. Turkiewicz^2
1VI Systems GmbH, Berlin, Germany
²Warsaw University of Technology, Poland
New generation of datacom standards require vertical cavity surface emitting lasers (VCSELs) operating at data rates beyond 50Gb/s in on-off-keying (NRZ) and pulse amplitude modulation (PAM4) formats. New Ethernet applications also require extended wavelength range enabling wavelength division multiplexing. We report on 850nm and 910nm VCSELs capable for data transmission at 50-100Gb/s. We show that single mode VCSELs are suitable for 60Gb/s NRZ transmission over 800m of OM5 multimode fiber. 56Gb/s 85°C VCSEL transmission over 100m of the most installed OM3 fiber is demonstrated.

Jesper Mørk
Towards high-speed Fano photonic switches
D. A. Bekele, A. Marchevsky, Q. Saudan, Yi Yu, M. Galili, L. K. Oxenløwe, K. Yvind, and J. Mørk
DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark, Lyngby, Denmark
Fano resonances occur as a result of the interference between a discrete mode and a continuum of modes. We have realized a Fano structure using a planar indium phosphide photonic crystal membrane device which consists of a point-defect nanocavity side-coupled to a line-defect waveguide. Compared to the traditional symmetric Lorentzian lineshape, the asymmetric Fano lineshape is characterized by having a transmission maximum and minimum in close spectral vicinity, leading to new opportunities in the areas of optical switching, lasing, sensing and narrow band filtering. Here, we present our recent work on optical switches which exploit the sharp asymmetric Fano lineshape in combination with strong carrier-induced nonlinear resonance shifts. This unique combination has enabled femtojoule per bit all-optical switching at tens of gigahertz operation speed. Particular focus is given to our experimental and theoretical investigations aiming at achieving faster recovery of the switches. Device physics, limitations and future perspectives will also be presented.

Raimondas Petruškevičius
Quasi-phase-matching method based on coupling compensation for second harmonic generation in GaN waveguides
R. Petruškevičius^1,2, D. Kezys^1,2, T. Malinauskas², M. Kolenda², and R. Tomašiūnas^2
1Center for Physical Sciences and Technology, Vilnius, Lithuania
²Institute of Photonics and Nanotechnology, Vilnius University, Lithuania
We report a novel quasi-phase-matching method based on coupling compensation for second harmonic generation in GaN/AlGaN waveguides on sapphire substrates. The proposed method can overcome limitations of periodically oriented GaN waveguides because of spatial periodic modulation of the light intensity along the propagation direction, rather than the conventional spatial periodic modulation of the nonlinear optical coefficients of GaN. The method can be realized by using a dual-planar or dual-ridge waveguide frequency doubler structure. This concept has the potential to open a new range of applications for broadband on-chip nonlinear frequency conversion.

Ana Quirce
VCSEL-based optical frequency combs: expansion of the optical span under arbitrary polarized optical injection
A. Quirce¹, C. de Dios², A. Valle³, and P. Acedo^2
1Vrije Universiteit Brussel, Brussels Photonics B-PHOT, Brussels, Belgium
²University Carlos III, Leganés, Madrid, Spain
³Instituto de Física de Cantabria (CSIC-University of Cantabria), Santander, Spain
We report on a theoretical study of the optical frequency combs (OFCs) generated by Gain-Switching Vertical-Cavity Surface-Emitting Lasers (VCSELs) under arbitrary polarized optical injection. Our results show that two orthogonally polarized sub-combs are obtained generating a wider overall optical comb for a certain angle between the linearly polarized optical injection and the direction of emission of the free-running VCSEL. This angle decreases as the injection strength increases. A characterization of the maximum expansion of the optical span of the overall comb has also been reported. Moreover, we have analysed the effect of the birefringence of the VCSEL in the expansion of the overall comb. We found that for VCSELs with large birefringence splitting, the maximum frequency enhancement is the optical span of the free-running comb, while for small birefringence splitting the maximum frequency enhancement is the birefringence splitting value.

Oksana Shramkova
Influence of an edge height on the diffracted EM field distribution
B. Varghese, O. Shramkova, V. Drazic, V. Allie, and L. Blonde
Technicolor R&D France, Rennes, France
The diffraction of light on the edge of a dielectric microstructure forms a tilted focused beam whose deviation angle depends on the index ratio between the structure material and host medium. The paper will demonstrate the existence of a critical height of a wavelength sized edge. This edge diffracts the incident light energy inside the higher index medium, as a specific field distribution. The analysis of this influence is done for optical and RF frequencies and identifies lobes in the resulting field distribution. The lobes repartition is driven by the critical height and its multiples. These EM patterns are evaluated in relation with the photonic nanojet phenomenon.

Miguel Urbaneja Torres
Transverse polarization light scattering in tubular semiconductor nanowires
M. A. Urbaneja Torres¹, A. Sitek^1,2, and A. Manolescu^1
1School of Science and Engineering, Reykjavik University, Reykjavik, Iceland
²Department of Theoretical Physics, Faculty of Fundamental Problems of Technology, Wroclaw University of Technology, Poland
We carry out numerical calculations of the scattering cross section of tubular semiconductor nanocylinders in the optical range. The scattering is investigated for the transversal incidence of light, i.e., along the diameter of the cylinder, with both transverse electric and transverse magnetic polarization. These subwavelength nanostructures support Mie resonances and, when the length of the cylinder is comparable to the wavelength, guided modes that can overlap with the Mie modes giving rise to sharp Fano resonances. We show that a varying internal radius affects each mode differently, allowing for an extra degree of freedom for tuning the spectral position of the resonant peaks.

Scott Watson
Applications of single frequency blue lasers
S. Watson¹, S. Gwyn¹, M. Knapp², S. Viola¹, G. Giuliano^1,3, T. J. Slight³, S. Stanczyk⁴, S. Grzanka⁴, C. Robinson², A. Yadav⁵, K. E. Docherty⁶, E. Rafailov⁵, P. Perlin⁴, S. P. Najda⁴, M. Leszczynski⁴, M. Haji², and A. E. Kelly^1
1University of Glasgow, School of Engineering, Glasgow, UK
²National Physical Laboratory, Teddington, Middlesex, UK
³Compound Semiconductor Technologies Global Ltd, Hamilton, UK
⁴TopGaN Lasers, Warsaw, Poland
⁵Aston University, Birmingham, UK
⁶Kelvin Nanotechnology Ltd, Glasgow, UK
Gallium nitride (GaN) sources are becoming a regular part of today’s world and are now key devices for lighting infrastructures, communications systems and quantum applications, amongst others. In particular, many applications have seen the shift from LEDs to laser diodes to make use of higher powers, higher bandwidths and increased transmission distances. Laser communication systems are well established, however there are applications where the ability to select a single emitted wavelength is highly desirable, such as quantum atomic clocks or in filtered communication systems. Distributed feedback (DFB) lasers have been realised emitting at a single wavelength where the grating structure is etched into the sidewall of the ridge. The main motivation in developing these lasers is for the cooling of ions in atomic clocks; however their feasibility for optical communications is also explored. Narrow linewidth lasers are desirable and this paper will explore how this is achieved. Data rates in excess of 1 Gbit/s have also been achieved in a directly modulated, unfiltered system. These devices lend themselves towards wavelength division multiplexing and filtered optical communications systems and this will be analysed further in the work presented here.

Alejandro Yacomotti
Intensity fluctuations and mode correlations in strongly coupled nanolasers
M. Marconi¹, F. Raineri¹, A. Levenson¹, A. M. Yacomotti¹, J, Javaloyes², C. Ciuti³, A. Biella³, N. Bartolo³, A. Pan⁴, A. El Amili⁴, and Y. Fainman^4
1Center for Nanoscience and Nanotechnology, CNRS/C2N UMR 9001, Palaiseau, France
²Departament de Fisica, Universitat de les illes Balears, Mallorca, Spain
³Laboratoire Matériaux et Phénomènes Quantiques, Université Paris Diderot, CNRS UMR 7162, Sorbonne Paris Cité, France
⁴Department of Electrical and Computer Engineering, University of California, San Diego, USA
We investigate second order correlation functions in a bimodal nanolaser and relate them with mode-intensity fluctuations. Measured joint probability distributions of the mode population imbalance reveal flat potential transitions, at the origin of large intermodal energy fluctuations. We observe a maximum of mode-intensity fluctuations at the switching point, consistent with a lower bound limit of the stochastic coupled-laser semiclassical model, for which second order cross correlation verify g⁽²⁾(0) ≥ 2/3.

Zeev Zalevsky
Nano-structures and plasmonic nano-antennas based devices for photonic sensing and data handling applications
M. Cohen^1,2, Y. Abulafia², R. Shavit³, A. Rudnitsky¹, S. Agdarov¹, and Z. Zalevsky^1,2
1Faculty of Engineering, Bar Ilan University, Ramat-Gan, Israel
²Nanotechnology Center, Bar Ilan University, Ramat-Gan, Israel
³Department of Electrical and Computer Engineering, Ben-Gurion University of the Negev, Beer-Sheva, Israel
In this presentation we will show novel designs to perform wide band sensing of light involving an array of nano structures and which are based upon enhanced conversion of incoming light into mechanical vibrations of the nano structures. We will discuss how such sensor can also be used as a photonic nano-transistor. In the second part of the talk we will present unique design of plasmonic nano-antennas having higher light to plasmons conversion efficiency and which are used for realizing wireless communication channels as a replacement for an existing interconnects of processing chips as well as for realization of plasmonic logic gates and transistors. A derivative of this technology is also used to perform secondary electrons imaging at the nano-scale.

NetOrch invited presentations:

Enrico Ghillino
Assessing the impact of design options for an optical switch in network routing impairments
E. Ghillino¹, P. Pasella⁴, R. Stoffer², D. Richards³, J. Patel¹, P. Mena¹, R. Scarmozzino¹, P. Bardella⁴, E. Virgillito⁴, D. Pilori⁴, A. Carena⁴, and V. Curri^4
1Synopsys, Inc., Ossining, USA
²Synopsys, Inc., Enschede, the Netherlands
³College of Staten Island, CUNY, Staten Island, NY, USA
⁴DET, Politecnico di Torino, Italy
In order to enable the maximum capacity in state-of-the art optical networks, a full orchestration with the physical layer is mandatory. Such an objective is obtained by abstracting network elements starting from the component design up to the networking management. To this purpose, a software (SW) environment which is vertically integrated across the networking layers is a mandatory support for engineering network infrastructure, or to virtually test the impact of a component design option on higher layer performance. Synopsys proposes an integrated SW environment for photonic integrated circuit (PIC) and system design that aims at satisfying this requirement: it is the integration of OptSim© – optical communication system, OptSim Circuit  – schematic-driven photonic circuit, OptoDesigner© – mask layout, and RSoft component design tools. These tools have proven to be reliable aids to virtually designing and estimating the performance of optical transmission systems and photonic chips. In this work, we rely on such an integrated SW environment to assess the impact on networking operations of design options for an optical switch in Silicon Photonics using Analog Photonics (AP) Process Design Kit (PDK) component library elements [1]. Specifically, we address the transmission impairments and consequent reduction in Quality-of-Transmission (QoT) implied by multi-hop routing in meshed optical networks. Using the vertical integration of the Synopsys SW environment, we analyze the considered optical switch and by simulation, we obtain a layer-0 abstraction. So, we simulate its propagation impact, assessing a QoT-degradation depending on the design option and also depending of the choice for the transmission technique. Finally, we derive the impact of network routing addressing the QoT degradation vs. number of traversed switches.

Jose-Luis Izquierdo-Zaragoza
Improved user experience by dynamic service handover and deployment on 5G network edge
J-J. Pedreno-Manresa¹, P. S. Khodashenas², J-L. Izquierdo-Zaragoza³, and P. Pavon-Marino^1
1Universidad Politécnica de Cartagena, Spain
²Fundació i2CAT, Barcelona, Spain
³Frequentis AG, Vienna, Austria
Novel end-to-end services are expected to emerge with the advent of 5G. In order to satisfy QoS/QoE requirements (e.g., lower latency, higher traffic volume and dynamicity, or availability) of those services, major changes on the network architecture. Technologies such as SDN and NFV, in conjunction with the edge-computing paradigm facilitate this transition, enabling the presence of cloud-enabled systems on mobile radio access networks. In this paper, we present a novel approach to handle Service Chaining handover, leveraging a joint orchestration between NFV and RAN domains

NOA invited presentations:

Vladimir Gordienko
Unwanted four wave mixing in fibre optical parametric amplifiers
V. Gordienko, M. A. Z. Al-Khateeb, F. M. Ferreira, A. D. Ellis, and N. J. Doran
Aston Institute of Photonic Technologies, Aston University, Birmingham, UK
Fibre optical parametric amplifiers (FOPA) rely on four wave mixing (FWM) and therefore offer the potential for ultra-low noise figures as well as a large wideband gain unrestricted to any specific wavelength. However, whereas efficient FWM is encouraged within FOPA to obtain amplification, some FWM products lead to signal distortion. In this paper we classify products of FWM generated in FOPA, evaluate the impact of unwanted FWM on FOPA performance and suggest how this impact can be mitigated.

Wladek Forysiak
Recent advances in discrete Raman amplifiers and their applications to wideband optical networks
W. Forysiak, M. A. Iqbal, L. Krzczanowicz, M. A. Z. Al-Khateeb, I. D. Phillips, and P. Harper
Aston Institute of Photonic Technologies, Aston University, Birmingham, UK
This presentation will focus on recent advances in the design of discrete Raman amplifiers (DRAs) and their potential application to wideband optical networks. The performance of dual-stage DRAs will be compared with conventional single-stage designs. The impact of Raman gain fibre nonlinearity in single-stage and dual-stage DRAs will be evaluated and compared with conventional EDFA based systems.

João Januário
High capacity unrepeatered optical transmission over hybrid fibers
J. C. S. S. Januário^1,2 and A. C. Bordonalli^2
1CPqD, Division of Optical Technologies, Campinas-SP, Brazil
²School of Electrical and Computer Engineering, State University of Campinas (UNICAMP), Campinas-SP, Brazil
Unrepeatered optical transmission over hybrid optical fiber is shown as an efficient solution to increase system capacity and reach. Together with a BER-orientated design, hybrid links with dedicated delivery fibers guarantee system performance improvement by handling at the same time with high nonlinear tolerance fibers and standard ones. The combination of both fiber types provides an attractive relation between system performance and cost, what gives a feasible solution for a sort of critical industry applications, beyond allowing to achieve capacity transmission records, such as the demonstrated 24x400G unrepeatered transmission over 443.1 km with 73.1 dB span loss.

Leo Spiekman
Polarization dependence in semiconductor optical amplifiers from a manufacturing perspective
L. H. Spiekman, Aeon Corp., Princeton, USA
The ideal semiconductor optical amplifier has 0 dB polarization dependent gain. The actual values obtained for devices in volume manufacturing determine process yield and therefore cost. We will discuss manufacturability and testability aspects of the fabrication of low-PDG SOAs in an industrial setting.

Mingming Tan
Distributed Raman amplification design for fibre nonlinearity compensation with mid-link optical phase conjugation
Mingming Tan, M. A. Z. Al-Khateeb, Tingting Zhang, P. Harper, and A. D. Ellis
Institute of Photonic Technologies, Aston University, Birmingham, UK
We demonstrate the design principles of distributed Raman amplifiers and propose the optimised configurations for both single and multi-fibre-span scenarios, which can provide near symmetric signal power distributions and therefore enhance the fibre nonlinearity compensation efficiency in long-haul fibre transmission systems using mid-link optical phase conjugation.

Feng Wen
Nonlinear-optical loop mirror (NOLM)-based all-optical multilevel amplitude regenerator
Biao Guo¹, Feng Wen¹, Baojian Wu¹, Feng Yang², and Kun Qiu^1
1Key Lab of Optical Fiber Sensing and Communication Networks, Ministry of Education, University of Electronic Science and Technology of China, Chengdu, China
²Lab of Holographic Optical Sensing, Marolabs Co., Ltd, Chengdu, China
This paper reviews the recent advances on nonlinear-optical loop mirror (NOLM)-based all-optical multilevel amplitude regenerator. Two different NOLM-based regenerator schemes, including the conventional single NOLM and the polarization-orthogonal continuous-wave-light-assisted NOLM (PC-NOLM) have been compared for the regenerative performance. The results show that the conventional NOLM regenerator gives a larger amplitude-noise handling capability on the low regenerative level, but the novel PC-NOLM scheme offering the same regenerative behaviours on multiple levels significantly improves the noise suppression on the high-order amplitude level. The uniform regenerative performance achieved in the PC-NOLM structure also results in a better EVM improvement, i.e. 2.33dB in the experiment.

Tianhua Xu
Limit of achievable Information rates in EDFA and Raman amplified transmission systems using nonlinearity compensation
Tianhua Xu^1,2,3, N. A. Shevchenko^3,4, Zhe Li⁵, Tiegen Liu¹, and P. Bayvel^3
1Tianjin University, China
²University of Warwick, Coventry, UK
³University College London (UCL), UK
⁴King's College London (KCL), UK
⁵Finisar Corporation, Horsham, PA, USA
Optical networks form an integral part of the world-wide communication infrastructure and nowadays over 95% of data traffic is carried over fibres. Erbium-doped fibre amplifiers (EDFAs) and Raman amplifiers have made it possible to extend the usable fibre bandwidth to increase the achievable capacity of optical communications in past decades to meet the ever-growing information rate demands. However, these amplification technologies are now viewed as limiting the accessible optical spectrum to ~5 THz and ~10–15 THz, respectively. Currently, the presence of Kerr effects in fibre channels has been largely regarded as the major bottleneck for enhancing achievable information rates of optical communications. Signal performance degradations due to fibre nonlinearities are more severe in the systems utilising larger transmission bandwidths, closer channel spacing and higher-order modulation formats. In this work, we will study the impact and compensation of Kerr effects to analyse the performance of long-haul optical fibre communication systems using EDFAs and Raman amplifiers. Achievable information rates of such ultra-wideband optical transmission systems will be discussed considering nonlinearity compensation and probabilistic shaping techniques.

Novel Glasses invited presentations:

Jean-Luc Adam
Microstructured chalcogenide glass fibers for infrared photonics
J-L. Adam¹, J. Trolès¹, L. Brilland², S. Venck², and R. Chahal^2
1Glasses & Ceramics Research Team, Institut des Sciences Chimiques de Rennes, UMR CNRS 6226, Université Rennes 1, France
²Selenoptics, Rennes, France
Compared to oxide based glasses, vitreous materials composed of chalcogen elements (S, Se, Te) show large transparency windows in the infrared. Indeed, chalcogenide glasses can be transparent from the visible up to 12 – 15 µm, depending on their compositions. This is due to the lower phonon energies of chalcogenides. In addition, chalcogenide glasses contain large polarisable atoms and external lone electron pairs which induce exceptional non-linear properties. Consequently, the non-linear properties of chalcogenide can be 100 or 1000 times as high as the non-linearity of silica. Optical non-linearity is further enhanced in optical fibers with microstructured geometries. The presentation deals with the latest results in terms of optical properties and applications of chalcogenide glass microstructured fibers, including the implementation of Mid-IR Quantum Cascade Laser pigtailing.

Rolindes Balda
Color-tunable upconversion luminescence in Er³⁺-Yb³⁺ co-doped sodium lutetium fluoride glass-ceramics
R. Balda^1,2, J. J. Velázquez³, G. Gorni³, I. Iparraguirre¹, M. Sedano³, M. Kochanowicz⁴, J. Zmojda⁴, D. Dorosz⁵, A. Durán³, M. J. Pascual³, and J. Fernández^6
1Departamento de Física Aplicada I, Escuela Superior de Ingeniería, Universidad del País Vasco UPV-EHU, Bilbao, Spain
²Materials Physics Center CSIC-UPV/EHU, San Sebastian, Spain
³Instituto de Cerámica y Vidrio (CSIC), Madrid, Spain
⁴Bialystok University of Technology, Bialystok, Poland
⁵AGH University of Science and Technology, Krakow, Poland
⁶Donostia International Physics Center DIPC, San Sebastian, Spain
In this work, the study of the near-infrared to visible up-conversion (UC) processes in transparent sodium lutetium fluoride glass ceramics in bulk and optical fibers co-doped with Er³⁺ and Yb³⁺ ions is reported. Intense UC green and red emissions due to (²H_11/2,⁴S_3/2)→⁴I_15/2 and ⁴F_9/2→⁴I_15/2 transitions respectively together with a more weak blue emission due to ²H_9/2→⁴I_15/2 transition has been observed under excitation at 980 nm. The dependence of the intensity ratio of the upconversion emissions on the excitation power intensity and Yb³⁺ concentration is investigated. Tunable UC luminescence from green to yellow can be obtained by varying the excitation power intensity which suggests that these materials can be promising candidates for applications in photonics devices.

Wilfried Blanc
Nanoparticles in optical waveguides: A toolbox to promote lasers, amplifiers and sensors
W. Blanc¹, M. Vermillac², L. Petit³, A. Lukowiak⁴, Zhuorui Lu¹, F. Mady¹, M. Benabdesselam¹, S. Chaussedent⁵, A. Mehdi⁶, and M. Ferrari^7,8
1Université Côte d'Azur, Institut de Physique de Nice, France
²High Performance Computing Institute, Ecole Centrale de Nantes, France
³Photonics Laboratory, Tampere University, Finland
⁴Institute of Low Temperature and Structure Research, PAS, Wroclaw, Poland
⁵Université d’Angers, LPhiA, France
⁶University of Montpellier, ICGM, CNRS UMR 5253, France
⁷CNR-IFN, CSMFO Lab. and FBK CMM, Povo, Trento, Italy
⁸Enrico Fermi Centre, Roma, Italy
The success of glass photonics are many, with a large spectrum of applications covering Information and Communication Technology, Health and Biology, Structural Engineering, and Environment Monitoring Systems, etc. A paradigmatic example is the development of the Erbium-Doped Fiber Amplifier (EDFA) allowing the raise of optical telecommunications and high speed internet. Silica glass is the most common glass used for photonics applications. However, certain of its characteristics may be detrimental for luminescence properties (low rare-earth solubility, high phonon energy, etc.). To overcome these limitations, the use of nanoparticles in optical waveguides is gaining large interest in modern photonic technology. Such waveguides would combine the advantages of silica (transparency, cost, chemical and mechanical durability, etc.) and the specific properties provided by the nanoparticles which encapsulate the rare-earth ions. In this paper, we will discuss on the opportunities offer for lasers and amplifiers thanks to the engineering of the spectroscopic properties. We will present also an emerging application: sensors based on high scattered fibers.

Maxime Cavillon
A materials approach toward the mitigation of nonlinearities in glass optical fibers
M. Cavillon^1,2, P. D. Dragic³, and J. Ballato^2
1Institut de Chimie Moléculaire et des Matériaux d’Orsay (ICMMO), Paris-Sud University, Orsay, France
²Center for Optical Materials Science and Engineering Technologies (COMSET) and the Department of Materials Science and Engineering, Clemson University, SC, USA
³Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, IL, USA
Power scaling in high energy fiber-based laser systems is limited by optical nonlinearities. Among the most detrimental nonlinearities are stimulated Brillouin and Raman scattering (SBS, SRS), nonlinear refractive index n2-related wave mixing phenomena, and transverse mode instability (TMI). As opposed to the complex micro-structured large mode area (LMA) fibers typically developed to mitigate these parasitic effects, this present work advocates another approach instead; namely attacking the nonlinearities through the enabling materials from which they originate. Hence, multicomponent core – silica glass cladding optical fibers fabricated using the molten core method will be presented and the role played by the glass dopants in the mitigation of nonlinearities discussed. More specifically, highlights will be made on multicomponent alkaline-earth (Sr, Ca) doped-silica fibers exhibiting concomitant reduction of >6 dB in the Brillouin gain coefficient, 1-2 dB in the Raman gain coefficient, and 2-3 dB in the thermo-optic coefficient relative to conventional silica fibers.

Martina Delgado-Pinar
In-fiber acousto-optics for the broadband measurement of the UV-induced refractive index change in photosensitive fibers
S. Rosales-Mendoza, M. Delgado-Pinar, E. Rivera-Pérez, J. Luis Cruz, A. Díez, and M. V. Andrés
Universidad de Valencia, Spain
In fiber acousto-optics has been demonstrated to be a versatile, highly sensitive technique that allows the characterization of the different parameters of single-mode or few-mode optical fibers, such as the fiber radius variation or the core refractive index, in a broadband wavelength range. In terms of variations of the core refractive index, the technique has a detection limit as low as 10^-8 in single-mode fibers, and short sections (~20 cm) of fiber are required to perform the measurements. The working principle of the technique relies on the fact that a variation in a fiber parameter shifts in wavelength the acousto-optic phase matching condition. Thus, by measuring this wavelength shift it is possible to evaluate the change in the parameter under study. In order to fabricate gratings in photosensitive fibers, the core refractive index is increased, typically, in 10^-5-10^-4. In this work we characterize by means the acousto-optic technique the refractive index change induced by UV radiation in different types of photosensitive fibers (H₂-loaded telecom fibers, boron co-doped fibers, or fibers with high concentration of Ge). Broadband characterization is performed in one go, using only one section of irradiated fiber. Our first results show that a refractive index change of 3×10^-5 is induced in H₂-loaded -telecom fiber (SMF28 from Corning) when the UV energy delivered to the fiber is 100 J/mm². Other types of photosensitive fibers and levels of energy are currently under test.

Dominik Dorosz
Luminescence and energy transfer in fluoroindate glasses doped with rare-earth
M. Kochanowicz¹, J. Zmojda¹, A. Baranowska¹, P. Miluski¹, J. Dorosz¹, M. Lesniak², M. Kuwik³, J. Pisarska³, W. A. Pisarski³, M. Sitarz², L. Mochalov^4,5, A. Nezhdanov⁴, M. Ferrari^6,7, G. Righini⁷, J. Dorosz¹, and D. Dorosz^2
1Bialystok University of Technology, Faculty of Electrical Engineering, Poland
²AGH University of Science and Technology, Faculty of Materials Science and Ceramics, Krakow, Poland
³University of Silesia, Institute of Chemistry, Katowice, Poland
⁴Lobachevsky State University of Nizhny Novgorod, Russia
⁵Nizhny Novgorod State Technical University n.a. R.E. Alekseev, Russia
⁶Istituto di Fotonica e Nanotecnologie IFN-CNR, CSMFO Laboratory, Povo-Trento, Italy
⁷Enrico Fermi Centre, Roma, Italy
This work reports the analysis of near-infrared luminescence of low phonon energy (510 cm^-1) fluoroindate glasses co-doped with Er³⁺/Tm³⁺ and Er³⁺/Ho³⁺ ions pumped by 796 nm, 980 nm laser diode, respectively. Due to donor-acceptor energy transfer and superposition of 1450 nm (Tm³⁺: ³H₄ → ³F₄) and 1550 nm (Er³⁺: ⁴I_13/2 → ⁴I_15/2) radiative transitions in glass co-doped with 0.1ErF₃/0.3TmF₃ a broadband emission in the range of third telecommunication window (FWHM = 152 nm, λ_exc = 796 nm) was obtained. Analysis of the spectroscopic properties of the 0.8ErF₃/1.4HoF₃ co-doped glass showed Er³⁺ → Ho³⁺ energy transfer and efficient sensitization of holmium ions leading to the 1.2 µm and 2 µm emission under 980 nm laser diode excitation.

Maurizio Ferrari
SiO₂-SnO₂ photonic glass-ceramics
L. T. N. Tran^1,2,3, D. Massella^4,1, R. Balda^5,6, S. Berneschi⁷, W. Blanc⁸, B. Boulard⁹, A. Chiappini¹, A. Chiasera¹, P. Dentella¹⁰, S. Eaton^10,11, J. Fernandez¹², M. Ferrari^1,13, J. Gates¹⁴, P. Gluchowski¹⁵, G. Ischia¹⁶, A. Lukowiak¹⁵, G. Nunzi Conti⁷, F. Prudenzano¹⁷, B. Rossi¹⁸, G. C. Righini^7,13, D. Zonta^1,2,19, and L. Zur^1
1IFN-CNR CSMFO Lab. and FBK Photonics Unit, Povo-Trento, Italy
²Department of Civil, Environmental and Mechanical Engineering, University of Trento, Italy
³Department of Applied Sciences, Ho Chi Minh City University of Technology and Education, Vietnam
⁴Department of Physics, University of Trento, Italy
⁵Departamento de Física Aplicada I, Escuela de Ingeniería de Bilbao, Universidad del País Vasco UPV-EHU, Bilbao, Spain
⁶Materials Physics Center CSIC-UPV/EHU, San Sebastian, Spain
⁷IFAC - CNR, Sesto Fiorentino, Italy
⁸Université Côte d'Azur, Institut de Physique de Nice, CNRS UMR7010, Nice, France
⁹IMMM UMR CNRS 6283, Université. du Maine, Le Mans, France
¹⁰Department of Physics, Politecnico di Milano, Italy
¹¹IFN-CNR, Milano, Italy
¹²Donostia International Physics Center DIPC, San Sebastian, Spain
¹³Museo Storico della Fisica e Centro Studi e Ricerche “Enrico Fermi”, Roma, Italy
¹⁴ORC, Optoelectronics Research Centre, University of Southampton, UK
¹⁵Institute of Low Temperature and Structure Research, PAS, Wroclaw, Poland
¹⁶Department of Industrial Engineering, University of Trento, Italy
¹⁷Politecnico di Bari, Italy
¹⁸Elettra - Sincrotrone Trieste, Trieste, Italy
¹⁹Department of Civil and Environmental Engineering, University of Strathclyde, Glasgow UK
Since the pioneering work of P. A. Tick, N. F. Borrelli. L. K. Cornelius, and M. A. Newhouse, titled “Transparent glass ceramics for 1300 nm amplifier applications” published in the J. Appl. Phys. on December 1995 the research regarding photonic glass-ceramics is fast growing. From this considerable number of published researches, covering a broad spectrum of applications, it appears that reliable fabrication techniques and realization of effective photonic devices are the two crucial pivots for an important advance in this glass-photonics area. The important results already obtained in rare earth -activated oxyfluoride, fluoride and silicate transparent glass ceramics are well known. Regarding silicate-based photonic glass-ceramic the binary system SnO₂-SiO₂ is really appealing when we look at the two above mentioned objectives. At the conference, a brief review of the state of art, consolidated results and recent advances in Erbium doped SnO₂-SiO₂ transparent glass-ceramics, obtained by sol-gel technology will be presented, and short-term perspectives will be outlined.

Alexander Fuerbach
Fabrication of gratings in mid-infrared compatible fibres via femtosecond laser direct inscription
A. Fuerbach, G. Bharathan, T. Fernandez, and M. Ams
Department of Physics and Astronomy, Macquarie University, Sydney, Australia
We report on our research into the fabrication of different types of gratings into optical fibres that are transparent at mid-infrared wavelengths. In particular, we focus on the inscription of fibre-Bragg gratings with parallel as well as tilted grating planes into zirconium and indium fluoride fibres. Spatially resolved Raman microscopy and electron probe microanalysis are used to investigate the physical mechanisms that underpin the induced refractive index modulation and the important influence of rare-earth ions in active fibres is discussed.

Jarosław Jędryka
Laser stimulated piezo-optical effects in chalcogenides
J. Jędryka¹, P. Rakus¹, I. V. Kityk¹, K. Ozga¹, and G. Myronchuk^2
1Institute of Optoelectronics and Measuring Systems, Czestochowa University of Technology, Poland
²Eastern European University, Luck, Ukraine
Laser stimulated effects in the chalcogenides under influence of multi-laser treatment have been discovered for the first time. The changes of the piezoelectricity have been explored and have been observed during the first 3 min of illumination. The changes of the effect for the cw and pulsed laser treatment are discussed. The relaxation of the processes is studied. The irreversible changes are explored. Possible application of the studies for the optical recording of information are given. The role of photo-thermal effects is shown.

Dobrosława Kasprowicz
Bifunctional Bi₃TeBO₉ crystals: Luminescence and µ-Raman investigation
D. Kasprowicz¹, T. Zhezhera¹, P. Głuchowski², M. Chrunik³, and A. Majchrowski^3
1Faculty of Technical Physics, Poznan University of Technology, Poland
²Institute of Low Temperature and Structure Research of Polish Academy of Sciences, Wrocław, Poland
³InstiInstitute of Applied Physics, Military University of Technology, Warsaw, Poland
A novel Bi₃TeBO₉ crystal is an excellent nonlinear optical material as well as an efficient host matrix for luminescent rare earth ions [1,2]. Investigated Bi₃TeBO₉ microcrystals doped with selected rare earth ions were synthesized by means of the modified Pechini method. The vibrational properties of Bi₃TeBO₉:Nd³⁺ were studied using µ-Raman spectroscopy [3]. The emission spectra show a strong luminescence at about 890 and 1062 nm (⁴F_3/2 ® ⁴I_9/2 and ⁴F_3/2 ® ⁴I_11/2, respectively). As a result, Bi₃TeBO₉:Nd³⁺ are very promising for NIR emitting phosphors with many potential applications in new generation of miniaturized optical devices.
[1] M. Xia, X. Jiang, Z. Lin, R. Li, J. Am. Chem. Soc. Journal, 2016, 138, 14190–14193.
[2] M. Daub, M. Krummer, A. Hoffmann, L. Bayarjargal, H. Hillebrecht, Journal, Chem Eur J, 2016, 22, 1–8.
[3] D. Kasprowicz, T. Zhezhera, A. Lapinski, M. Chrunik, A. Majchrowski, A.V. Kityk, Ya. Shchur, J. Alloys Comp., 2018, 782, 488–495.

Andriy Kityk
Mesoporous alumina- and silica-based crystalline nanocomposites with tailored anisotropy: Methodology, structure and properties
A. V. Kityk¹, A. Andrushchak², Ya. Shchur³, V. T. Adamiv⁴, O. Yaremko², M. Lelonek⁵, S. A.Vitusevich⁶, O. Kityk⁷, R. Wielgosz⁷, W. Piecek⁸, M. Busch⁹, K. Sentker⁹, and P. Huber^9
1Faculty of Electrical Engineering, Czestochowa University of Technology, Poland
²Institute of Telecommunications, Radio Electronics and Electronic Technics, Lviv Polytechnic National University, Ukraine
³Institute for Condensed Matter Physics, Lviv, Ukraine
⁴O.G. Vlokh Institute of Physical Optics, Lviv, Ukraine
⁵SmartMembranes GmbH, Halle, Germany
⁶Institute of Bioelectronics (ICS-8), Jülich, Germany
⁷Energia Oze Sp. z o.o., Konopiska, Poland
⁸Military University of Technology, Warsaw, Poland
⁹Institute of Materials Physics and Technology, Hamburg University of Technology, Germany
We present several recently synthesized nanocomposites consisting of liquid crystals as well as an organic molecular crystal embedded into the nanochannels of mesoporous alumina and silica. As liquid-crystalline mesogens achiral, nematogen and chiral cholesteric guest molecules infiltrated into nanochannels by spontaneous imbibition were chosen. The molecular ordering inside the nanochannels, which can be tailored by modifying the surface anchoring, was characterized by optical polarimetry (linear and/or circular birefringence) in combination with X-ray diffraction. For the synthesis of the solid crystalline nanocomposites ferroelectric triglycine sulfate (TGS) nanocrystals were deposited into the nanochannels by slow evaporation of saturated water solutions imbibed into the porous hosts. Their textural and physicochemical properties were explored by x ray diffraction, scanning electron microscopy and dielectric techniques.

Julien Lumeau
Thin-film optical elements based on chalcogenide materials
A. Bourgade, F. Lemarquis, T. Begou, and J. Lumeau
Aix Marseille Univ., CNRS, Centrale Marseille, Institut Fresnel, Marseille, France
Thin-film components based on chalcogenide layers will be demonstrated. These component include volume diffractive optical elements based on photo-induced refractive index change or silver photodissolution in As₂S₃ layers and ultra-uniform bandpass filters based on photosensitive chalcogenide spacers. Theoretical study and design, experimental demonstration and final complete characterization of various optical elements will be presented.

Leonid Mochalov
New generation of materials for the Near-Mid IR sensors based on lead chalcogenides
L. Mochalov^1,2, A. Logunov², T. Sazanova², and V. Vorotyntsev^2
1University of North Carolina at Charlotte, North Charlotte, USA
²Nizhny Novgorod State Technical University n.a. R.E. Alekseev, Russia
The sensitivity of lead-based chalcogenide materials (PbS, PbSe, PbTe, PbSTe and PbSeTe) and their commercial applicability are strongly dependent on the preparation techniques and the purity of the initial substances. For these reasons, as many research groups all over the world as industrial firms show a great interest in the ongoing development of various techniques of these materials such as electrodeposition, spray pyrolysis, photo-accelerated chemical deposition, microwave-heating, and chemical bath deposition. However, all the existing preparation technologies feature a few substantial disadvantages. First of all, liability of lead-based chalcogenide materials to disproportion and crystallization leads to a high roughness of the surface of final thin films and the lack of chemical and structural uniformity that in its turn sufficiently influence on the sensitivity of the detectors, stability of their work and on the ratio signal/noise. Secondly, the thermal activation of chemical interaction between precursors causes the contamination of the final materials from materials of setup or due to incomplete conversion of the initial substances. Finally, commercially available initial substances do not provide the proper optical quality of the IR optical materials due to they contain a great amount of impurities optically active in IR range like oxygen, carbon and hydrogen. These impurities are non-limiting in the commercial materials. They also leads to the sharp decreasing of the detectors sensitivity and overheating because of strong selective absorption in the detector working range 1-3 microns. In this connection, the development of the principal novel approach based on plasma initiation of the initial substances by electron impact in low-temperature plasma discharge at low pressure in combination with development of technologies of deepest purification of the initial substances – elemental Pb, S, Se and Te would be key elements of the novel technological approach.

Pavel Peterka
Enhanced pump absorption efficiency in coiled and twisted double-clad fibers for fiber lasers
P. Peterka¹, P. Koška¹, A. A. Jasim¹, N. Kanagaraj¹, J. Aubrecht¹, M. Kamrádek^1,2, O. Podrazký¹, F. Todorov¹, I. Kašík¹, and P. Honzátko^1
1Institute of Photonics and Electronics of the Czech Academy of Sciences, Prague, Czech Republic
²Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Czech Republic
High-power operation of fiber lasers was enabled by the invention of cladding-pumping in a double-clad fiber structure. Pump absorption is enhanced by broken circular symmetry of inner cladding cross sections and by mode-scrambling of the pump modes by unconventional fiber coiling. However, theoretical studies were limited to the assumption of a straight fiber until recently, when the rigorous model accounting for double-clad fiber bending and twisting was described. It was found that squeezing of the effective area of the pump radiation due to fiber bending plays important role in cladding-pump absorption enhancement. We review results of numerical modelling of pump absorption in various types of double-clad fibers, e.g., with cross section shape of hexagon, stadium, and circle; two-fiber bundle (so-called GTWave fiber structure) a panda fibers are also analyzed. The presented results can have practical impact in construction of fiber lasers: with pump absorption efficiency optimized by our new model (the other models did not take into account fiber twist), the double-clad fiber of shorter length can be used in the fiber lasers and amplifiers. In such a way the harmful influence of background losses and nonlinear effects can be minimized. Less demanding cladding-mode-strippers can be used.

Laeticia Petit
Persistent luminescent glasses prepared using the direct doping method
U. Aryal¹, N. Ojha¹, A. Veber¹, L. Petit¹, M. Lastusaari², T. Trautvetter³, R. Mueller³, and J. Ueda^4
1Photonics Laboratory, Physics, Tampere University, Finland
²University of Turku, Department of Chemistry, and Turku University Center for Materials and Surfaces (MatSurf), Finland
³Leibniz Institute of Photonic Technology, Jena, Germany
⁴Graduate School of Human and Environmental Studies, Kyoto University, Japan
Persistent luminescence (PeL) or afterglow is defined as light emission lasting from seconds to even days after stopping the excitation source, typically ultraviolet (UV) light. The first glass ceramics were successfully obtained with persistent luminescence using the so called “Frozen sorbet method”. In this technique, the persistent luminescence was obtained by the precipitation of Eu²⁺,Dy³⁺-doped SrAl₂O₄ crystals in the glass within the SrO-Al₂O₃-B₂O₃ system. However, this technique cannot be used to develop new glasses as the crystals precipitate in the glass using the ions from the glass. Later, glasses with persistent luminescence were successfully obtained by adding PeL microparticles (MPs) in the glass batch prior to the glass melting. As the MPs need to be thermally stable at the glass melting temperature, this technique cannot be applied to all glass systems. Since then, great progress has been made in the preparation of PeL glasses with various compositions. In this presentation, we will review our work on the development of glasses in different glass systems, exhibiting persistent luminescence at different wavelengths in the visible. We explain, first how to prepare such glasses using the direct doping method. We discuss the challenges related to the direct doping method, especially, the stability of the MPs in the glass, which is sensitive to the melting/sintering conditions but also to the glass system.

Francesco Prudenzano
Design of ultra-wideband Yb:Er:Tm:Ho co-doped germanate glass devices
M. C. Falconi¹, D. Laneve¹, V. Portosi¹, S. Taccheo², and F. Prudenzano^1
1Department of Electrical and Information Engineering, Politecnico di Bari, Italy
²Laser Group, Swansea University, UK
The synthesis of multiple rare earth co-doped glasses has attracted large interest during the last decade since it promises the fabrication of active devices with ultra-wideband light emission/amplification. Unfortunately, the high number of spectroscopic parameters, pertaining to each rare earth ion transition and to the energy transfer phenomena among the different rare earth ions, makes the optimization of the rare earth doped optical glasses and devices not trivial. In particular, the multiple rare earth doped glass design is further complicated because the energy transfer phenomena nonlinearly depend on the dopant concentration levels and the ion population levels. In this work, to overcome this problems, the particle swarm optimization (PSO) approach is proposed to globally handle the gain spectrum of a Yb:Er:Tm:Ho co-doped germanate glass [1]. An accurate numerical code, based on the nonlinear rate equations [2-4], is ad-hoc developed and the gain coefficients close to the different wavelengths 1.55 µm, 1.8µm and 2.05 µm, are calculated assuming optical pumping at 980 nm. The model takes into account the main light matter interaction mechanisms i.e. the absorption and stimulated emission, the radiative decays and the energy transfer phenomena [1]. The spectroscopic parameters used in the simulations are taken by experimental data reported in literature in order to perform an investigation able to provide design guidelines. The optimized Yb:Er:Tm:Ho co-doped germanate glass is then considered as basis material for the design of fiber amplifiers/lasers operating in the1.5 µm- 2.0 µm wavelength range with the aim to obtain a flat ultra-wideband gain spectrum.
[1] A. Albalawi, M. Kochanowicz, J. Zmojda, P. Miluski, D. Dorosz, and S. Taccheo, Fluorescence spectrum of an Yb:Er:Tm:Ho doped germanate glass, in Laser Congress 2018 (ASSL), OSA Technical Digest, paper ATu2A.4, Boston, 4-8 Nov. 2018.
[2] M. C. Falconi, G. Palma, F. Starecki, V. Nazabal, J. Trolès, J.-L. Adam, S. Taccheo, M. Ferrari, and F. Prudenzano, Dysprosium-doped chalcogenide master oscillator power amplifier (MOPA) for mid-IR emission, Journal of Lightwave Technology, vol. 35, no. 2, pp. 265-273, Jan. 2017.
[3] M. C. Falconi, G. Palma, F. Starecki, V. Nazabal, J. Troles, S. Taccheo, M. Ferrari, and F. Prudenzano, Design of an efficient pumping scheme for mid-IR Dy³⁺:Ga₅Ge₂₀Sb₁₀S₆₅ PCF fiber laser, Photonics Technology Letters, vol. 28, no. 18, pp. 1984-1987, Sep. 2016.
[4] M. C. Falconi, D. Laneve, M. Bozzetti, T. T. Fernandez, G. Galzerano, and F. Prudenzano, Design of an efficient pulsed Dy³⁺:ZBLAN fiber laser operating in gain switching regime, Journal of Lightwave Technology, vol. 36, no. 23, Dec. 2018.

Elena Romanova
Evanescent waves in glassy chalcogenide structures for remote spectroscopic sensing of environment
E. Romanova¹, S. Korsakova¹, D. Zhivotkov^1,2, A. Rozhnev^1,3, and V. Shiryaev^4
1Saratov State University, Russia
²Ruđer Boškovič Institute, Zagreb, Croatia
³Saratov Branch of the Institute of Radio-Engineering and Electronics of RAS, Russia
⁴Institute of Chemistry of High Purity Substances of RAS, Russia
Evanescent waves propagating in optical fibers can collect and deliver information about absorption spectra of an external medium. We analyse peculiarities of evanescent modes and whispering gallery modes that can be excited in a single-index multimode chalcogenide fiber immersed into an absorbing medium. Dispersion properties of the modes allow for creation of a combined sensing element/frequency converter.

Vladimir Shiryaev
Development of high-purity REE-doped chalcogenide glasses for mid-IR fiber optics
V. Shiryaev¹, E. Karaksina¹, T. Kotereva¹, A. Velmuzhov¹, A. Plekhovich¹, and E. Boyko², and A. Shushunov^2
1G. G. Devyatykh  Institute of Chemistry of High-Purity Substances of  the Russian Academy of Sciences, Nizhny Novgorod, Russia
²N. I. Lobachevski Nizhny Novgorod State University, Russia
In this paper, experimental results on the development of high-purity chalcogenide glasses and optical fibers for passive and active mid-IR fiber optics are presented. Novel Ge-As-Se-Ga and Ge-Sb-Se-Ga glass compositions are proposed and studied. Methods for the synthesis of high-purity glasses, host and doped with Pr(3+), Er(3+), Tb(3+) and Dy(3+) ions, are developed. The thermal, optical and luminescent properties of novel chalcogenide glasses are investigated. Glasses with a low tendency to crystallization, different glass transition temperatures (Tg = 220-356°C), and a strong mid-IR luminescence are produced. On the basis of prepared glasses, single-index, suspended-core and core-clad optical fibers are fabricated and investigated. Successful testing of these materials for the development of infrared optics devices is demonstrated.

Sławomir Sujecki
Multimode selenide-chalcogenide glass fiber-based MIR spontaneous emission sources with shaped output spectrum
S. Sujecki^1,2, L. Sojka¹, D. Jayasuriya², M. Shen², Z. Tang², E. Barney², D. Furniss², T. M. Benson², and A. B. Seddon^2
1Department of Telecommunications and Teleinformatics, Faculty of Electronics, Wroclaw University of Science and Technology, Poland
²George Green Institute for Electromagnetics Research, The University of Nottingham, UK
Mid-infrared (MIR) light sources operating in the range of wavelengths spanning from 3000 nm to 25000 nm have many potential applications in the fields of medicine, pollution monitoring, biology, agriculture and security. This is because the resonant oscillation frequencies of many molecular bonds fall within MIR wavelength range. For instance, in medicine the application of MIR light would help to improve the effectiveness of cancer diagnostics. It was demonstrated recently that a near infrared semiconductor laser pumped multimode chalcogenide glass fibre can be used for generation of broadband emission within the MIR wavelength range. In this contribution it is shown that broadband emission stretching from 2000 nm up to 6000 nm can be achieved when using selenide-chalcogenide glass. It is also shown experimentally that by appropriate selection of pumping wavelengths and powers the shape of the output spectrum can be varied to suit a particular application.

Caroline Vigreux
Functionalization of chalcogenide thin films: First step towards optical bio-sensors
C. Vigreux¹, B. Robert^1,2, R. Escalier¹, L. Courthéoux¹, A. Pradel¹, B. Varga², M. Martin-Fernandez², C. Gergely², A. Mehdi³, and R. Bendoula^4
1ChV team, ICGM, UMR 5253, Université de Montpellier, France
²Biophotonics team, L2C, UMR 5221, Université de Montpellier, France
³CMOS team, ICGM, UMR 5253, Université de Montpellier, France
⁴ITAP group, IRSTEA, UMR 1201, Montpellier, France
The final objective of the project is to develop optical bio-sensors for the early detection of plant diseases. The idea is that the light signal at the output of the sensors would be modified by fixing the spores to their surface, as illustrated below. In parallel with the work of creating guiding structures such as interferometers, resonators, couplers, etc., based on thin chalcogenide layers of the GeSeTe ternary system, we are considering different strategies for the functionalization of these layers: by adhesion peptides developed by the "phase display" technology already validated for ZnSe for example, or with silanes or mercaptos.

Lidia Zur
New lanthanide source from e-waste to fabricate active photonic structures
L. Zur¹, R. Tomala², A. Hojenska², W. Strek², S. Aldabe Bilmes³, S. J. L. Ribeiro⁴, J. Rodriguez⁵, A. Bouajaj⁶, A. Chiasera¹, M. Ferrari^1,7, and A. Lukowiak^2
1IFN-CNR CSMFO Lab. and FBK Photonics Unit, Povo, Trento, Italy
²Institute of Low Temperature and Structure Research, PAS, Wroclaw, Poland
³Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Buenos Aires, Argentina
⁴Institute of Chemistry, São Paulo State University, Araraquara-SP, Brazil
⁵Universidad Nacional de Ingenieria, Lima, Peru
⁶Laboratory of Innovative Technologies, LTI, ENSA–Tangier, University Abdelmalek Essaâdi, Tangier, Morocco
⁷Museo Storico della Fisica e Centro Studi e Ricerche “Enrico Fermi”, Roma, Italy
Looking at the literature of the last years it is evident that rare-earth-activated optical structures represent the technological pillar of a huge of photonic applications covering Health and Biology, Structural Engineering, Environment Monitoring Systems, and Quantum Technologies. Increasing demand for rare earths (lanthanides) and an increasing amount of waste electrical and electronic equipment (WEEE, e-waste) deposited at landfills, especially in developing countries, challenge the researchers to develop the efficient recovery procedures of lanthanides from e-waste. In other words, it became important for economic and environmental reasons. At the conference, the state of art and the aim of the activity will be presented. The research covers the development of methodologies to extract lanthanides (and other metals) from e-waste, where specific nanostructured materials for metals extraction and separation are used. Later, the quality of recovered lanthanide compounds is evaluated through chemical analysis. Additionally, the synthesis of phosphors based on recovered compounds as well as their characterization will be discussed and the comparison between recovered and commercially available materials will be outlined.

OMT invited presentations:

Ali Belarouci
Morphological effects in photonic integrated nanojet
A. Belarouci¹, O. Hudz¹, M. Calvo², P. Rojo Romeo¹, and R. Orobtchouk^2
1Lyon Institute of Nanotechnologies INL, CNRS UMR 5270, Ecole Centrale de Lyon, Université de Lyon, Ecully, France
²Lyon Institute of Nanotechnologies INL, CNRS UMR 5270, INSA de Lyon, Université de Lyon, Villeurbanne, France
We report a study of the shape-dependent optical response of a photonic nanojet created by a single Si_xN_y microdisk illuminated by a waveguide. High intensity sub-wavelength spots and low divergence nanojets are observed at the telecommunication wavelengths. Light scattered from the disk is observed by imaging from above. The electromagnetic distributions inside and outside the microdisk are calculated by using finite-difference-time-domain method and compared to the experimental image. We demonstrate that small morphology variations can have a major impact on the optical properties of the entire system. These results deepen our understanding between the disk morphology and its optical response and provide insight toward potential applications in high-resolution optical imaging, biophotonics, and optical data storage.

Georges Boudebs
Nonlinear refraction and absorption coefficients of transparent materials illuminated by strong light beams
M. Chis¹, Hongzhen Wang², C. Cassagne², C. Ciret², and G. Boudebs^2
1ESAIP, St-Barthélemy d'Anjou Cedex, France
²Laboratoire de Photonique d'Angers, LPHIA, EA 4464, SFR MATRIX, University Angers, France
We explore the effective nonlinear (NL) optical response of transparent materials illuminated by strong light beams with two different setups to study the influence of the numerical aperture (NA) corresponding to the collecting lens on the measured coefficients in the open and closed aperture Z-scan transmittance. For that, we have reproduced experiments in CS₂ at 532nm in the picosecond regime. It is found that measurement of high order NL coefficients is possible up to a limit defined by the self-focusing of light inside the cell and that stimulated light scattering is not relevant to explain alone the saturation behaviour that occurs in the NL refraction measurements. Indications are given for future Z-scan experiments that may clarify the new boundary conditions to be respected for the measurement.

Juan Bueno
Deconvolution method for multiphoton microscopy: An application to thick ocular tissues
J. M. Bueno¹, R. M. Martínez-Ojeda¹, L. M. Mugnier², and P. Artal^1
1Laboratorio de Óptica, Universidad de Murcia, Spain
²ONERA/DOTA, Université Paris Saclay, Châtillon, France
Multiphoton (MP) microscopy of thick biological tissues is limited by the presence of aberrations and scattering. In addition, living samples impose an additional limit due to uncontrolled movements. To overcome these constraints, deconvolution methods are proposed as an alternative to well-established adaptive optics procedures. A marginal blind deconvolution approach for the reconstruction of MP images of both ex-vivo and living ocular tissues is shown and discussed. The quality of the images reconstructed by this method is compared to that of the original ones in terms of the inherent artefacts and of the achieved resolution, among other criteria.

Gabriella Cincotti
Correlative multimodal approach based on optical near-field and topographic imaging to characterize the morphology of ESKAPE pathogen bacteria at nanoscale
G. Cincotti¹, M. Lucidi¹, S. G. Stanciu², D. E. Tranca², A. M. Holban^2,3, L. Nichele¹, and G. A. Stanciu^2
1Department of Engineering, University Roma Tre, Italy
²Center for Microscopy-Microanalysis and Information Processing, University Politehnica of Bucharest, Romania
³Microbiology Department, Faculty of Biology, University of Bucharest, Romania
Microscopy techniques such as confocal laser scanning microscopy (CLSM), multiphoton excitation microscopy (MPM) or coherent anti-Stokes Raman scattering microscopy (CARS), are nowadays extensively utilized to study biological species and represent the “backbone” of many important imaging applications in biology and medicine. However, the resolution of these far-field techniques is limited by diffraction to half the wavelength of the excitation light which impedes an accurate understanding of important structures and processes taking place at nanoscale. Super-resolution techniques overcome this limitation via different ingenious concepts and strategies, and techniques such as fluorescence-Photoactivation Localization Microscopy (f-PALM), Stochastic Optical Reconstruction Microscopy (STORM), or Stimulated Emission Depletion (STED) microscopy are now capable to routinely achieve optical resolutions of ~50 nm, but they rely on fluorescence labelling which results in various limitations. Apertureless scattering near-field optical microscopy (ASNOM) can resolve in a label-free manner optical details <10 nm, and the underlying architecture of techniques in this family allows the simultaneous acquisition of atomic force microscopy (AFM) datasets, which is useful for placing nanoscale optical data into a registered topographic context. However, most of the studies that have been carried out until now with ASNOM were targeted on the characterization of basic and advanced materials, and due to the limited body of work targeting biological samples, ASNOM images acquired in such experiments are in most cases difficult to interpret. Moreover, although ASNOM and AFM images are usually displayed side by side in studies that involve these two techniques, an exact model to explain how the information extracted with these two distinct modalities are correlated is still not available at the time being. In this paper, we contribute to this field, by proposing a model for correlated multimodal imaging (CMI) that combines ASNOM data collected on multiple harmonics (amplitudes and phases) with AFM topography data, to create a composite image that allows a to better characterize the morphology of bacterial cells. A complete and detailed characterization of bacterial species plays a fundamental role in many biomedical studies, related to bacterial infection diagnosis and treatment. In particular, we consider pathogens of the ESKAPE group, that are involved in hospital- and community-associated infections, with a high capability to resist to different antibiotics.

Massimo De Vittorio
Tapered fibers for optogenetics: Gaining spatial resolution in deep brain regions by exploiting angle-selective light injection systems
A. Balena^1,2, M. Bianco^1,2, F. Pisano¹, M. Pisanello¹, L. Sileo¹, B. Spagnolo¹, B. Sabatini³, M. De Vittorio^1,2, and F. Pisanello^1
1Istituto Italiano di Tecnologia (IIT), Center for Biomolecular Nanotechnologies, Arnesano (Lecce), Italy
²Dipartimento di Ingegneria dell’Innovazione, Universita` del Salento, Lecce, Italy
³Department of Neurobiology, Howard Hughes Medical Institute, Harvard Medical School, Boston, USA
This work describes a method to inject light into tapered optical fibers (TFs) in order to achieve site-selective and wide-volume optical control of neural activity with a single optical setup. The method relies on a Galvanometric – Resonant mirrors scan head, employed to inject light into the fiber to: (i) select a specific subset of guided modes obtaining localized illumination or (ii) to scan between the different guided modes at high-rate to obtain full NA-like light injection on time scales >0.2ms. This is shown by analysing the light emission profiles from the TF with different voltage biases applied to the Galvanometric and the Resonant mirrors, and comparing them with a standard Full NA light-injection. With the aim to find the experimental parameters to obtain efficient Full NA – like emission profile, the Emission Length and the First Emission Diameter of TFs were extracted and compared with an ideal wide-volume emitter. Both Galvanometric and Resonant scanners methods shown a good agreement with the reference values of the standard Full NA injection, allowing neuroscientists to switch from site-selective to wide-volume illumination using a single optical setup.

Eleonora Frau
Characterization of biological liquids by modulated 3D cross-correlation dynamic light scattering
E. Frau and S. Schintke
Laboratory of Applied NanoSciences (COMATEC-LANS), Department of Industrial Technologies, HEIG-VD, University of Applied Sciences and Arts Western Switzerland, Yverdon-les-Bains, Switzerland
The deep biomedical knowledge reached in the past decades in many fields of medicine and biology has been accompanied by continuous technological progress in measurement instrumentation and analysis techniques. This development is important also to improve the characterization and the understanding of the interactions between nanoparticles and biological liquids, due to emerging applications such as drug delivery, bioimaging, biosensing, diagnostics and photothermal therapy.  In this study, we characterize the interaction between mouse serum and gold nanoparticles (NPs) and nanorods (NRs) by Modulated 3D Cross-correlation Dynamic Light Scattering (DLS), in order to demonstrate that this technique can be applied to the investigation of complex biological liquids. The analysis of the size distribution of the hydrodynamic radius reveals three different contributions from particles motion, associated to rotation, translation and agglomerates. Moreover, we show that the interaction between Au NPs or NRs and mouse serum depends on the aspect ratio of the Au particles. These results are promising for deepening the knowledge on proteins-nanoparticles interaction, for laboratory-based experiments as well as for sensing and diagnostic applications and nanoparticles based medical therapy.

Marco Pisanello
Modeling brain tissue scattering for optical neural interfaces
E. Maglie^1,2, M. Pisanello¹, F. Pisano¹, A. Balena^1,2, B. Spagnolo¹, B. L. Sabatini³, M. De Vittorio^1,2, and F. Pisanello^1
1Istituto Italiano di Tecnologia (IIT), Center for Biomolecular Nanotechnologies, Arnesano (Lecce), Italy
²Dipartimento di Ingegneria dell’Innovazione, Universitá del Salento, Lecce, Italy
³Department of Neurobiology, Howard Hughes Medical Institute, Harvard Medical School, Boston, USA
The possibility to optically control and monitor neural activity with optogenetic methods has generated the need for new implantable devices to deliver and collect light from neural tissues. This is being accompanied by a set of methods that allow to numerically predict and experimentally test how light emitted by implanted optoelectronic devices, semiconductor waveguides and optical fibers behave in a highly scattering medium like the brain tissue. After discussing the most common scattering models, this work focuses on how emission and collection properties of optical fibers implanted the brain can be estimated. To assess photometry efficiency fields of an optical fiber implanted in a turbid medium, we combine numerically evaluated light emission and collection fields in presence of scattering. This approach can help to complement current knowledge on the influence of tissue scattering on the optical properties of implanted photonics devices, providing additional information for the design of optical bidirectional neural interfaces.

Adrian Podoleanu
Gabor fusion master slave optical coherence tomography
A. Podoleanu¹, R. Cernat¹, A. Bradu¹, M. Marques¹, N. Moller Israelsen², O. Bang², S. Rivet³, P. Keane⁴, D. Garway-Heath⁴, and R. Rajendram^4
1Applied Optics Group - School of Physical Sciences, University of Kent, Canterbury, UK
²Technical University of Denmark, DTU Fotonik - Fiber Sensors and Supercontinuum, Kgs. Lyngby, Denmark
³Université de Bretagne Occidentale, EA 938 Laboratoire de Spectrométrie et Optique Laser, Brest, France
⁴NIHR Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK
The communication refers to a solution to repetitive change of focus when performing swept source (tunable laser) interferometry. There are now swept source (SS) lasers exhibiting several meters coherence lengths for robotic navigation and cubic meter OCT. However, micron lateral resolution can only be achieved with sufficient high numerical aperture interface optics, in which case the depth range falls below sub-millimeter. Repetition of data collection is needed for each new focus (Gabor). This counteracts the advantage of SS-OCT, that of delivering information from all depths in one scan via a Fourier Transform (FT). To eliminate the time wasted on producing data from all axial range, Master Slave (MS) OCT is proposed, that delivers data while laterally scanning the beam, from a single depth of interest, in real time. We present combination of MS-OCT with 4 repetitions of acquisitions each for a different focus position, to acquire high resolution volumes and en‑face OCT from different targets. By combining the two techniques, Gabor filtering and Master/Slave-OCT, a powerful imaging instrument is demonstrated. The MS technique allows simultaneous display of three categories of images in one frame: multiple depth en-face OCT images, two cross-sectional OCT images and a confocal like image obtained by averaging the en-face ones. We also demonstrate the superiority of MS-OCT over its FT based counterpart when used with a Gabor filtering OCT instrument in terms of the speed of assembling the fused volume.

Gabriel Popescu
Quantifying myelination at the individual axon scale using color spatial light interference microscopy (cSLIM)
M. Fanous^1,2, M. P. Caputo³, L. A. Rund⁴, M. Kandel^1,5, Young Jae Lee^2,6, C. Best-Popescu^2,6, R. W. Johnson^3,4, T. Das⁷, M. J. Kuchan⁸, and G. Popescu^1,2,5
1Quantitative Light Imaging Laboratory, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, USA
²Department of Bioengineering, University of Illinois at Urbana-Champaign, USA
³Division of Nutritional Sciences, University of Illinois, USA
⁴Laboratory of Integrative Immunology and Behavior, Department of Animal Sciences, University of Illinois, USA
⁵Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, USA
⁶Cellular Neuroscience Imaging Laboratory, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, USA
⁷Abbott Nutrition, Discovery Research, Columbus, OH, USA
⁸Abbott Nutrition, Strategic Research, Columbus, OH, USA
Deficient myelination in the internal capsule of the brain is associated with neurodevelopmental delays, particularly in high-risk infants such as those born small for gestational age (SGA). MRI technology has been effective at measuring brain growth and composition but lacks myelin specificity and is low resolution. There is an unmet need for developing of new quantitative approaches that are rapid and precise, which can complement MRI and provide insight into the pathology of deficient myelination and efficacy of nutritional interventions. To meet this challenge, we developed Color Spatial Light Interference Microscopy (cSLIM), a method that is cable of generating refractive index maps of stained specimens. Using paraffin embedded brain tissue sections, stained myelin was segmented from a bright-field image and, using a binary mask, those portions were quantitatively analyzed by cSLIM. Due to cSLIM’s nanoscale sensitivity to optical path lengths and independence with respect to the stain intensity, we quantified subtle variations in myelin density at the single axon scale.

Mohamed Rafi
Effect of gallium on graded Cu(In_1−xGa_x)S₂ thin films for solar cells prepared by chemical spray pyrolysis
M. Rafi^1,2, B. Hartiti¹, A. Ridah², P. Thevenin³, and B. Mari^4
1Laboratory of Industrial Engineering, Mohammed VI, International Academy of Civil Aviation, Morocco
²Laboratory LIMAT. FS, Ben M'sick, Morocco
³Laboratory LMOPS, Université de Lorraine, Metz, France
⁴Grup d'Optoelectrònica i Semiconductors, Departament de Física Aplicada-ETSED, Universitat Politècnica de València, Spain
The chalcopyrite semiconductor Cu(In_1−xGa_x)S₂ (0 < x < 1),) is a potential candidate for absorber material in thin-film solar cells due to higher absorption coefficient (~10⁵ cm⁻¹), higher radiation stability, non-toxicity and to direct band gap adjustable. In this work, the ternary CIGS thin films have been deposited by chemical spray pyrolysis on preheated glass substrates using different concentrations of gallium in the spray solutions. The dependence structural, morphological, compositional and optical properties of the CIGS thin films have been studied using X-ray diffraction (XRD), Raman scattering measurements, scanning electron microscopy (SEM), optical absorption techniques and photoluminescence (PL) spectra respectively. The X-ray spectra reveal that the CuIn_1-xGa_xS₂ thin films are of chalcopyrite crystal structure with a highly (112) preferential orientation. The main XRD peaks showed a noticeable shift to higher diffraction angles with increasing Ga content, which was attributed to Ga atoms substituting for In atoms in the chalcopyrite structure. The grain size of CIGS films decreased with increasing Ga content presumably, and pores formed on the surface. Raman spectroscopy analysis indicates that the sprayed thin films are grown with two different structures, Cu-Au (CA)-ordered phase and chalcopyrite (CH). The Optical properties was calculate from the measured spectral transmittance Tλ and reflectance Rλ allow us to determine the direct band gap energy value which increases by increasing the Ga content and it is in the range 1.41 – 1.50 eV, indicating that Cu(In_1−x Ga_x)S₂ compound has an absorbing property favorable for photovoltaic applications.

George Stanciu
Correlative imaging using a multimodal microscopy system for investigations at micro and nano scales
G. A. Stanciu¹, D. E. Tranca¹, S. G. Stanciu¹, R. Hristu¹,  C. Stoichita¹, and J. M. Bueno^2
1Center for Microscopy-Microanalysis and Information Processing, University Politehnica of Bucharest, Romania
²Laboratorio de Óptica, Universidad de Murcia, Spain
In our work we present some correlated images at micro and nanoscale that we have obtained using different laser scanning microscopy techniques integrated in a multimodal microscopy system. The multimodal system includes several microscopy techniques working in far field and in near field. The main advantage of the system is connected with the possibility to image the same area of the sample at micro and nanoscale so that a correlation between the images could be made and an explanation of the images at nanoscale can be done. By overlaying the structural images obtained from different techniques, a more comprehensive view of different samples can be obtained. In addition, the possibility to see the same sample area at micro and nano scales offers the possibility to make a connection between the different elements of the structures.

Fang-Wen Sun
Noninvasive electromagnetic field sensing at nanoscale
Fang-Wen Sun, Xiang-Dong Chen, and Guang-Can Guo
CAS Key Lab of Quantum Information, University of Science and Technology of China, Hefei, China
Light-matter interaction is the foundation of studies in nanophotonics and nanoelectronics. It can modify the local electromagnetic field. The detection of the local electromagnetic field is necessary for further fundamental researches and applications. An ideal nanoscale-electromagnetic-field sensing system should satisfy the requirements of high spatial resolution, low perturbation, high sensitivity and multifunction. Here, we explored the application of non-invasive optical far-field super-resolution microscopy to electromagnetic field sensing at nanoscale. The nitrogen vacancy centers in diamond were used as multifunctional probes to investigate various optical and electrical properties of nanostructures. The polarization-dependent local density of states and electrical conduction were detected with a resolution of 49 nm (1/10 of the diffraction limit) by combining the probes’ quantum state manipulation. With such a super-resolution technique, the fidelity of sensing was also improved comparing with the results of traditional diffraction-limited optical microscopy. Based on this method, we expect that a multifunctional quantum nanoscope can be built for the future studies of nanoscience.

Antonela Toma
Advances in fractal analysis of the biological tissues images obtained by using far field and near field microscopy techniques
A. Toma, D. E. Tranca, R. Hristu, and G. A. Stanciu
Faculty of Applied Sciences, University Politehnica of Bucharest, Romania
Fractals are geometric patterns with geometrical and topographical features that are repeated in miniature on smaller length scales. The fractal dimension measures the rate of addition of structural detail with increasing magnification serving as a quantifier of complexity. By using a multimodal microscopy system we have images in fluorescence as we as in label free microscopy techniques. We used fractal analysis to have quantitative information regarding biological tissues. The images were obtained using far field and near field techniques integrated in a multimodal microscopy system.

OSCto5G invited presentations:

Victoria Bueno
A use case of shared 5G backhaul segment planning in an urban area
J. L. Romero-Gázquez, F-J. Moreno-Muro, M. Garrich, M-V. Bueno Delgado, P. S. Khodashenas, and P. Pavón Mariño
Universidad Politécnica de Cartagena, Spain
This work presents a case study for the network planning of a 5G backhaul for ultrafast mobile broadband in a dense urban area. The study is fed by estimated population density data and real geographical layout coming from a Spanish city (Cartagena, around 220,000 population). The layout includes current locations of 4G base stations, which are assumed to place new 5G macrocells as well, and real positions of lamp posts. The study assumes (i) an agreement among mobile operators to share the 5G network infrastructure or similar and (ii) a hypothetical agreement with the city hall, where the 5G deployment could make use of the lamp posts for planning microcells, covering the city with a broadband 5G access. An algorithm has been implemented to solve the dimensioning problem as an Integer Linear Program. The deployment cost is assumed to be proportional to the microcells to install in the scenario under study. Deployment statistics like the number of microcells per macrocell and the ratio of traffic served over them are also analysed. The results can help mobile network operators to drive their strategic investment decisions.

Alexis Dowhuszko
Integration of optical and satellite communication technologies to improve the cache filling time in future 5G edge networks
A. Dowhuszko, M. Shaat, and A. Pérez-Neira
Centre Tecnològic de Telecomunicacions de Catalunya (CTTC/CERCA), Castelldefels, Barcelona, Spain
Caching is an enabler to avoid congestion and delay in the backhaul links of future 5G networks. The basic idea behind this concept consists in estimating the content that would be most likely requested by the end users served by each edge node and, after that, make a pro-active placement of those files during the traffic off-peak hours. Optical wired/wireless terrestrial links support a high point-to-point data rate but, when the same content needs to reach different destinations, parallel unicast transmissions are needed. On the other hand, satellite systems provide a lower link-level data rate but can easily implement a multicast transmission due to their wide-area coverage. In this paper, a resource allocation strategy that determines the most convenient way to transport the different content using both terrestrial (optical) and satellite (radio) technologies is proposed. Simulation results show that the placement time can be notably reduced in a hybrid terrestrial-satellite backhaul network, particularly in case of bad weather that impacts the data rate of the wireless optical links. The effect of the file popularity distribution and the number of 5G edge nodes on the delivery time is also studied in detail. Keywords: Free space optical, satellite systems, content delivery, caching, Zipf distribution, hybrid backhaul.

Ramón Durán
Joint VNF-provisioning and virtual topology design in 5G optical metro networks
L. Ruiz, R. J. Durán, I. de Miguel, N. Merayo, J. C. Aguado, P. Fernández, R. M. Lorenzo, and E. J. Abril
Optical Communications Group, Universidad de Valladolid, Spain
5G technology will provide networks with high-bandwidth, low latency and multitenancy. The integration of computing and storage resources in the edge of the fronthaul network, i.e., Mobile Edge Computing (MEC), will allow to instantiate some Virtual Network Functions (VNF) in those computing resources. The backhaul of 5G networks will be based on optical technology, in particular WDM, due to its high capacity and flexibility. In this paper, we analyse the problem of VNF-provisioning in a network equipped with MEC resources and with a WDM network connecting the mobile edge nodes. In contrast to previous proposals, the method decides where VNFs must be instantiated but also the design of the virtual topology for the WDM backhaul network in order to reduce the service blocking rate and the number of resources in operation (and, thus, the energy consumption).

Hamzeh Khalili
Introducing terrestrial satellite resource orchestration layer
H. Khalili, P. S. Khodashenas, D. Guija, and S. Siddiqui
Software Networks Area (SNA), Fundació i2CAT, Barcelona, Spain
Satellite communications is an essential building block of 5G technology to ensure delivery of 5G promises such as ubiquitous connectivity, enhance mobile broadband (eMBB) and massive machine type communication (mMTC). Service providers require seamless connectivity between terrestrial and satellite system, considering the best transport options available according to bandwidth, latency, network conditions and other application-specific requirements. The interworking between terrestrial and satellite is well recognized and promoted in the standardization bodies like 3GPP and ETSI. Full integration foresees coexistence of satellite system, with the radio networks (core and access) as well as computational resources expanded from the core to the network edge. A suite of orchestration of heterogeneous resources is fundamental enabler to realize this vision. This paper focuses on the management and orchestration of heterogeneous resource integrated with MANO-like framework for rapid provisioning of network services. The proposed architecture provides a user-friendly single point of interaction for all stakeholders in the ecosystem, i.e. terrestrial and satellite operators as well as 5G vertical providers, where they can launch and manage end-to-end 5G services. The system allows easy integration of multiple applications (e.g. virtual 5G Core, virtual caching, etc.) as well as solutions provided by radio and satellite vendors (e.g. satellite gateway, small cells, etc.).

Harri Saarnisaari
5G NR over satellite links: Evaluation of synchronization and random access processes
H. Saarnisaari and C. Morais de Lima
University of Oulu, Finland
Integration of 5G new radio (NR) with satellite technology is an ongoing task in the standardization bodies. One integration goal is to use the 5G NR in satellite systems. Since 5G NR was designed as a terrestrial system, its direct suitability has to be evaluated. Initial synchronization and random access process are among the topics. This paper provides an overview of these processes and points out problematic point and proposed solutions. Especially processing of the synchronization signal block that contains also information for access to the devices is considered where challenge is the possibly large Doppler frequency shift of satellite channels that exceeds that of the terrestrial systems by a large margin. Furthermore, random access process that includes PRACH transmission, its guard interval, timing advance calculation and transmission and well as some process related timers, is considered.

OWW invited presentations:

Ernesto Ciaramella
TOWS: Introducing optical wireless for satellites
E. Ciaramella¹, G. Cossu¹, E. Ertunc¹, L. Gilli¹, A. Messa¹, M. Rannello¹, M. Presi¹, A. Sturniolo¹, F. Bresciani², and E. Pensa^2
1Scuola Superiore Sant'Anna, Italy
²Thales Alenia Space, Italy
We present the high-level approach of TOWS Project, which will design, realize and demonstrate new implementations of optical wireless systems supporting satellite applications. The TOWS systems should allow for seamless integration into present satellite payloads, reducing the weight and material budget, removing cabled connections. The paper presents an overview of the target results and key issues that will be addressed by the TOWS partners.

Abhishek Dixit
CDMA and error control codes in free space optical communication networks
Sonali, A. Dixit, and V. K. Jain
Bharti School of Telecommunication Technology and Management, Indian Institute of Technology Delhi, New Delhi, India
Free space optical (FSO) communication based networks offer a high bandwidth but are constrained due to atmospheric turbulence which limits their data rate. In addition, the FSO channel has a long coherence time which limits the error correction capabilities of the conventional error control codes (ECCs). In this paper, we propose a new modulation technique which we refer to as symbol-interleaved code division multiple access (CDMA) where the orthogonal codes are formed using bit across symbols. However, the symbol-interleaved CDMA increases the packet delay which is also an important metric. Thus, we complement the symbol-interleaved CDMA with information available from feedback channel which optimizes the interleaving depth (which is how many symbols are considered for coding) depending upon the channel characteristics.

Jan Latal
Measurement of the influence of total rainfall on a modulated optical beam within the laboratory FSO system
J. Latal, J. Vitasek, M. Bojko, L. Hajek, A. Vanderka, Z. Wilcek, J. Kolar, and T. Stratil
VSB-Technical University of Ostrava, Faculty of Electrical Engineering and Computer Science, Department of Telecommunications, Ostrava, Czech Republic
This article deals with the study of measurements of total rainfall simulated in laboratory environment for a modulated optical beam within FSO systems. The aim of our study was to demonstrate how significant dependence of influence of total rainfall is due to communications in the laboratory within FSO system. We used different types of modulated light sources (lasers) working on different wavelengths within FSO systems. The integral part of our work was a detailed analyse of performance of simulated atmospheric transmission conditions which have an effect on the laboratory FSO system.

Alessandro Messa
Optical wireless systems for high energy physics: Design and characterization
A. Messa¹, G. Cossu¹, A. Sturniolo¹, W. Ali^1,3, L. Gilli¹, P. G. Verdini², R. Dell’Orso², A. Basti², F. Palla², and E. Ciaramella^1
1Scuola Superiore Sant’Anna, Pisa, Italy
²Istituto Nazionale Fisica Nucleare, Pisa, Italy
³Now with Department of Engineering Science, University of Oxford, UK
We presented the design, system test and irradiation tests of the opto-electronics components of a 10 Gb/s OWC system proposed for the future update of CMS at CERN. We designed the system using a VCSEL as the transmitter and a PIN photodiode with a proper lens. Its measured tolerance to misalignment is around ±1 mm (at Bit Error Rate of 10^-12), then it does not require an active tracking system because. Both VCSEL and PD performance strongly reduced after the exposure to the massive proton irradiation.

Anand Srivastava
Optimized user association for indoor hybrid Li-Fi Wi-Fi network
R. Ahmad and A. Srivastava
Department of Electronics and Communication, IIIT-D, New Delhi, India
There is an exponential increase in the wireless data consumption due to the growing demands of mobile services and applications which results into overloading of the existing Wi-Fi network. One possible solution is to exploit the available visible light spectrum for communication i.e. light fidelity (Li-Fi). Li-Fi utilizes the illumination light emitting diodes (LEDs) for high-speed wireless communication. As the electromagnetic spectrum of Li-Fi does not overlap with Wi-Fi, they both can coexist to form a hybrid Li-Fi-Wi-Fi network. In hybrid Li-Fi Wi-Fi network, Li-Fi will support high data rate due to its huge unlicensed bandwidth whereas the Wi-Fi would take care of coverage at the blind spots. The performance of a hybrid system, significantly depends upon the user association and resource allocation strategies. In this paper, a downlink hybrid system with single Wi-Fi access point (AP) and four Li-Fi APs is considered and an optimization algorithm is implemented in order to determine an optimal user association strategy, which will maximize the overall system throughput while maintaining the fairness among the users. The performance of the proposed system is compared against conventional received signal strength (RSS) based method and the results are reported in terms of the system throughput and user satisfaction.

Jan Vitásek
Comparison of properties of white LED and blue LED with external phosphor layer
J. Vitasek, T. Stratil, Z. Wilcek, J. Kolar, and M. Hub
Faculty of Electrical Engineering and Computer Science, Department of Telecommunications, VSB-Technical University of Ostrava, Czech Republic
This article deals with comparison of illumination and communication properties of white LED (5500K) and blue LED with external phosphor layer. At the start, the illumination properties of phosphors (internal, external) were measured after excitation by square signal. Based on these values, suitable frequencies of communication signal were determined. Further, frequency of modulation signal was increased with regard on final white signal. The voltage transmission was also calculated for both white light sources.

Mike Wolf
On the DC balance of multi-level PAM VLC systems
M. Wolf and M. Haardt
Communications Research Laboratory, Ilmenau University of Technology, Germany
Lighting requirements and their impact on visible light communication (VLC) systems based on multi-level pulse-amplitude modulation are discussed. We will show that the moving average of the signal must not fluctuate too much. Two solutions are presented. One is based on a simple extension of the well-known 5B6B line coding to codes with M-ary symbols. The other is based on the so-called Hadamard-coded modulation. Closely related to the topic of DC balance is the resistance of the received signal to high-pass filtering. The impact of such filtering on multi-level PAM systems with frequency domain equalization is investigated. We will show that the demand for flicker-free lighting can easily be met with line codes. Together with an equalization, which has to be used for multi-level PAM anyway, the AC coupling at the receiver is no problem either. The feasibility of an adaptive modulation is also discussed.

PAM invited presentations:

Kyungwon An
Experimental realization of superabsorption by phase-correlated atoms in a cavity
Kyungwon An, Department of Physics and Astronomy, Seoul National University, Seoul, Korea
Cooperative emission of phase-correlated atoms or superradiance has been observed in atomic cold ensembles, Bose-Einstein condensates and low-temperature solid-state systems. The Tavis-Cummings Hamiltonian accounting for superradiance also suggests cooperative absorption by phase-correlated atoms or superabsorption, which if realized would enable weak-signal sensing as well as efficient light-energy harvesting in photovoltaics and photosynthesis. However, the superabsorption has not been observed in experiments yet. Here, we report experimental realization of superabsorption by using the time-reversed process of the coherent superradiance. Phase-correlated atoms in the same superposition state were prepared by using a nano-hole array atomic beam aperture placed in front of a high-Q cavity. The time reversal was then achieved by preparing the phase of the superposition state of atoms opposite to that of the atoms which would generate the coherent superradiance with its phase the same as that of an input field. The intracavity field was depleted by the superabsorption much faster than by the ordinary absorption of ground-state atoms. We experimentally observed that the number of photons completely absorbed for a given time interval was proportional to ????^2, a definitive evidence for superabsorption, in contrast to the ordinary absorption proportional to ???? the number of atoms in the cavity.

Trevor Benson
Evolutionary methods in clinical diagnostics
N. Malinowska¹, S. Phang², D. Furniss², A. B. Seddon², T. M. Benson², and E. Beres-Pawlik^1
1Wroclaw University of Science and Technology, Poland
²Mid-Infrared Photonics Group, George Green Institute for Electromagnetics Research, University of Nottingham, UK

Hasnaa El Ouazzani
Enhanced infrared fingerprint detection using Helmholtz-like nanoresonators
H. El Ouazzani¹, A. Fabas¹, J.-P. Hugonin², R. Haidar^1,3, J.-J. Greffet², and P. Bouchon^1
1ONERA-The French Aerospace Lab, Palaiseau, France
²Laboratoire Charles Fabry, Institut d’Optique Graduate School, CNRS, Université Paris-Saclay, Palaiseau, France
³Ecole Polytechnique, Département de Physique, Palaiseau, France
This work consists of studying and characterizing nanostructures for detection in the infrared region. According to their engineering and their architecture, they make possible to manipulate light by modifying the optical response and exalt the light-matter interactions. Here, we study a new type of optical nanoantennas called optical Helmholtz nanoresonator by analogy with acoustic. This resonator, which made of a tiny slit above a larger cavity, is able to capture and concentrate the light in very small volumes, and to manipulate its properties such as polarization and absorption [1-3]. However, the experimental implementation of this resonator is complicated due to the difficulty of its manufacture, which led us to simplify this structure by proposing a new geometry with similar properties and which we called Helmholtz-like nanoresonator. So, we used this concept to exalt the infrared signature of the 2,4-dinitrotoluene (DNT) molecule by demonstrating the capabilities of the surface-enhanced infrared absorption (SEIRA) effect to detect the chemical signature emanating from this molecule. Promising results are obtained and opens interesting perspectives for the use of these Helmholtz type resonators as specific and sensitive sensors of molecules.
[1] P. Chevalier, P. Bouchon, R. Haïdar, and F. Pardo, Appl. Phys. Lett. 105, 071110(2014).
[2] P. Chevalier et al, P. Bouchon, J.J Greffet, J.L. Pelouard, R. Haïdar, and F. Pardo, Phys. Rev. B 90, 195412 (2014).
[3] P. Chevalier et al., Appl. Phys. Lett. 112, 171110 (2018).

Takehiro Fukushima
Fully illuminated modes in a Penrose unilluminable room microcavity
T. Fukushima, Department of Information and Communication Engineering, Okayama Prefectural University, Japan
In 1958, Roger Penrose proposed an interesting cavity geometry which always has unilluminable regions wherever a point light source is set in the cavity as a mathematical model of illumination problems. The cavity is called ‘Penrose unilluminable room.’ Our ray dynamical simulation revealed that the cavity has three kinds of chaotic ray trajectories which are confined in different regions. In this case, one can expect resonance modes which are confined in different limited regions corresponding to each chaotic ray trajectory from the viewpoint of ray-wave correspondence. We carried out mode analysis of a Penrose unilluminable room microcavity based on the finite element method and found these expected resonance modes. However, we also found fully illuminated resonance modes which spreads widely in the entire cavity contrary to our expectation. In my talk, I will discuss the formation mechanism of these interesting resonance modes based on our numerical calculation results.

Guoping Lin
Optical orbital angular momentum in a monolithic nonplanar ring oscillator
Guoping Lin, Yaqin Cao, and Zehuang Lu
MOE Key Laboratory of Fundamental Physical Quantities Measurement, Hubei Key Laboratory of Gravitation and Quantum Physics, PGMF and School of Physics, Huazhong University of Science and Technology, Wuhan, China
Solid-state monolithic nonplanar ring oscillator (NPRO) is a well-known platform to generate narrow-linewidth laser sources. Light in an NPRO at the lasing wavelength is usually confined by a few total internal reflections within one round-trip. High reflection coating on one of the surfaces is often used to enable direct free-space coupling. In this communication, we present recent results on the direct generation of kHz-level linewidth Laguerre-Gaussian beams carrying orbital angular momentum (OAM) in an Nd:YAG NPRO platform. Vortex beams featuring crystal-like OAM are also generated and investigated. These results can find potential applications in optical tweezers and high-capacity optical communications.

Gregory Morozov
Quantum mechanical analogue of optical microdisk resonators
R. P. Meeten and G. V. Morozov
Scottish Universities Physics Alliance (SUPA), Institute of Thin Films, Sensors and Imaging, University of the West of Scotland, Paisley, UK
The complex wavenumber plane furnishes us with a natural way to seek resonant modes of optical cavities [1,2]. In this work we present the solution of the quantum mechanical analogue of an optical microdisk resonator. The rich dynamical behaviour of the states is shown for a circular potential barrier in response to continuous variations of the parameters of the potential. In particular, the flows of the resonances go to limit points which are zeros of Hankel and Bessel functions in wave number coordinates. The technique of examining flow dynamics used in this work will prove useful in the analysis of optical resonators, particularly those made of metamaterials.
[1] C.P. Dettmann, G.V. Morozov, M. Sieber, H. Waalkens, “Internal and external resonances of dielectric disks,” Europhys. Lett. (EPL), vol. 87, 34003, Aug. 2009.
[2] C.P. Dettmann, G.V. Morozov, M. Sieber, H. Waalkens, “Systematization of all resonance modes in circular dielectric cavities”, in Proc. ICTON 2009, Tu.C4.6, Jul. 2009.

Aleksander Smirnov
Nonlinear generation of multipolar radiation in Mie-resonant nanoparticles
A. I. Smirnov, Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia
I. Volkovskaya, D. Smirnova, and A. Smirnov
Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia
We study multipolar composition of the second harmonic generation from Mie-resonant dielectric nanoparticles made of noncentrosymmetric materials. With the use of the Lorentz lemma, we analytically derive excitation coefficients of the nonlinearly generated multipoles in spherical nanoparticles optically driven by the magnetic dipole mode. Multipolar radiation properties are then validated in the direct full-wave numerical calculations.  The developed description can be useful for design of nonlinear optical nanoantennas.

Silvia Soria Huguet
Optomechanical oscillations in microbubble resonators: Enhancement, suppression and chaotic behaviour
X. Rosello-Mecho¹, G. Frigenti^2,3, M. Delgado-Pinar¹, M. V. Andrés¹, G. Righini^2,4, G. Nunzi Conti^2,4, and S. Soria^2
1Dep. Of Applied Physics and Electromagnetism- ICMUV, University of Valencia, Burjassot, Spain
²CNR-IFAC Institute of Applied Physics “N. Carrara”, Sesto Fiorentino, Italy
³Laboratorio Europeo di Spettroscopia Nonlineare (LENS) - Università degli Studi di Firenze, Italy
⁴Centro Studi e Ricerche “E. Fermi”, Rome, Italy
Whispering gallery mode resonators (WGMR) have attracted a great interest in the last decade. WGMR have been fabricated in different geometries, solid and hollow, spherical, toroidal, and bottled shaped. Hollow spherical WGMR or microbubble resonators (MBR) are the last arrived in the family of resonators. The approach used for their fabrication is based on surface tension driven plastic deformation on a pressurized capillary, similar to glassblowing. Using such technique we are able to fabricate large surface area and thin spherical shells with high quality factor (Q), quite dense spectral characteristics and anomalous total dispersion. MBR are efficient phoxonic cavities that can sustain both optical photons and acoustic phonons. It has been demonstrated that MBR can be used to study Kerr comb patterns and Stimulated Brillouin Scattering (SBS). Radiation pressure is another mechanism that also leads to excitation of acoustic phonons with lower frequencies, in the range of hundreds of kHz to tens of MHz in the case of silica MBR. In the case of radiation pressure, the acoustic waves are surface waves with an efficient transfer of the optical energy into the mechanical modes. Thin walled MBR exhibit strong optomechanical effects like toroids due to their low stiffness and very dense spectral characteristics. The frequency of such oscillations occurs very close to the mechanical eigenfrequencies of the cavity. The nonlinear dynamics that originates from the coupling of mechanical and optical modes of the MBR can cause that both modes, optical and mechanical, evolve from periodic to chaotic oscillations. MBR show two different routes to chaos: periodic and quasi-periodic doubling bifurcation and a set of discrete lines into a continuum, and finally a continuum. For very large MBR, the transition to chaos is abrupt. We have also studied the temporal behavior of the cavity, the coexistence and the suppression of the oscillation while generating Kerr combs. The oscillation suppression occurs when the light is coupled to the resonance with red detuning (the pump has a lower frequency than the resonance). In this case, we generate photons in other resonant modes equally spaced (four wave mixing processes). Nonlinear phenomena were observed when the cavity was vibrating for low pump power and more than one mode was oscillating in the cavity. For high pump power only one mechanical mode was oscillating, in agreement with Braginsky theory and the optomechanical parametrical oscillations continue as long as the CW pump power is maintained. We also demonstrated the chaos transfer between two optical fields mediated optomechanically such that both fields follow the same route to chaos. Our experiments confirm that the chaotic vibration is an intrinsic property of the cavity that does not require external modulation or feedback, that it is not limited to a specific geometry.

Misha Sumetsky
Theory, fabrication, and new applications of optical bottle microresonators
M. Sumetsky, Aston Institute of Photonics Technologies, Aston University, Birmingham, UK
The optical microresonators reviewed in this presentation are called bottle microresonators because their profile often resembles an elongated spheroid or a microscopic bottle. These resonators are commonly fabricated from an optical fibre by variation of its radius. Generally, variation of the bottle microresonator (BMR) radius along the fibre axis can be quite complex presenting, e.g., a series of coupled BMRs positioned along the fibre. The elongation of BMRs along the fibre axis enables their several important properties and applications not possible to realize with other optical microresonators. First, I will review the BMR theory, which includes their spectral properties, theory of resonant transmission of light through BMR microresonators coupled to transverse waveguides, and theory of nonlinear BMRs. Next, I will consider the fabrication methods of BMRs. Finally, I will discuss the applications of BMRs which include miniature BMR delay lines and lasers, nonlinear and optomechanical BMRs, BMR for quantum processing, and BMR sensors.

Yun-Feng Xiao
Microcavity-enhanced surface nonlinear optics
Yun-Feng Xiao, State Key Laboratory for Mesoscopic Physics and School of Physics, Peking University, Beijing, China
Confinement and manipulation of photons using microcavities have triggered intense research interest in both fundamental and applied photonics for more than two decades. Prominent examples are ultrahigh-Q whispering gallery microcavities which confine photons by means of continuous total internal reflection along a curved and smooth surface. The long photon lifetime, strong field confinement, and in-plane emission characteristics make them promising candidates for enhancing light-matter interactions on a chip. In the first part of this talk, I will introduce some representative photonics applications of ultrahigh-Q microcavities. In the second part, I will introduce the second-order nonlinear optics induced by symmetry breaking at the surface of an ultrahigh-Q silica microcavity under a sub-milliwatt continuous-wave pump. By dynamically coordinating the double-resonance phase matching, a second harmonic is achieved with a conversion efficiency of 0.049% W⁻¹, 14 orders of magnitude higher than that of the non-enhancement case.

PICAW invited presentations:

Theoni Alexoudi
Waveguide frontend designs for beam transforming applications
D. Ketzaki¹, G. Patsamanis², T. Lamprecht³, K. Vyrsokinos², and T. Alexoudi^1
1Department of Informatics, Center for Interdisciplinary Research and Innovation, Aristotle University of Thessaloniki, Greece
²Department of Physics, Center for Interdisciplinary Research and Innovation, Aristotle University of Thessaloniki, Greece
³vario-optics AG, Heiden, Switzerland
Wavelength Selective Switches (WSS) appear as the key building blocks towards realizing next generation flexible-grid WDM optical networks. Lately, research attempts have shifted from pure bulky free-space WSS implementations to hybrid approaches where waveguide-based frontends (WFEs) are combined with a limited number of free-space components, enabling in this way the beam transforming functionality with lower cost and reduced footprint. In this communication we present our recent work on InP and Polymer waveguide-based frontend designs towards implementing an integrated waveguide frontend for hybrid WSSs.

Carlos Alonso-Ramos
Harnessing sub-wavelength and symmetry engineering for the implementation of high-performance silicon Bragg grating filters
D. Oser¹, X. Le Roux¹, F. Mazeas², D. Pérez-Galacho³, D. Benedikovic¹, E. Durán-Valdeiglesias¹, V. Vakarin¹, O. Alibart², P. Cheben⁴, S. Tanzilli², L. Labonté², D. Marris-Morini¹, E. Cassan¹, L. Vivien¹, and C. Alonso-Ramos^1
1Centre de Nanosciences et de Nanotechnologies, CNRS, Orsay, France
²National Research Council, Ottawa, K1A 0R6, Canada
³Université Côte d’Azur, CNRS, Institut de Physique de Nice, France
⁴ITEAM research institute, Universitat Politècnica de València, Spain
Bragg filters stand as a key building blocks of the silicon-on-insulator (SOI) photonics platform, allowing the implementation of advanced on-chip signal manipulation. However, achieving narrowband Bragg filters with large rejection levels is often hindered by fabrication constraints and imperfections. Here, we present a new generation of high-performance Bragg filters that exploit subwavelength and symmetry engineering to overcome bandwidth-rejection trade-off in state-of-the-art implementations. We experimentally show flexible control over the width and depth of the Bragg resonance. These results pave the way for the implementation of high-performance on-chip pump-rejection filters with a great potential for Si-based quantum photonic circuits.

Lucio Andreani
Slow-light modulators in silicon waveguides gratings
L. C. Andreani¹, M. Passoni¹, D. Gerace¹, G. C. R. Devarapu^2,3, and L. O’Faolain^2,3
1Physics Department, University of Pavia, Italy
²Centre for Advanced Photonics and Process Analysis, Cork Institute of Technology, Ireland
³Tyndall National Institute, Cork, Ireland
Integrated Mach-Zehnder modulators are key components in silicon photonic devices, which rely on a reverse-biased p-n junction to modulate the optical signal via a change of the waveguide refractive index. Reducing their energy consumption is a crucial issue towards applications of silicon photonics to optical communication. In this presentation, we describe the design of slow light structures consisting of silicon grating waveguides, which have an increased group index close to the photonic band edge. Also, we discuss how the design of p-n junctions affects matching between the optical field mode and the depletion region, in order to improve the modulation efficiency and to reduce the energy dissipation per bit of the modulator.

Stéphane Calvez
Controlled oxidation of III-V semiconductors for photonic devices
S. Calvez, G. Lafleur, O. Stepanenko, A. Arnoult, A. Monmayrant, H. Camon, and G. Almuneau
LAAS-CNRS, Toulouse, France
The oxidation of III-V semiconductors is a crucial technological process in the mass-volume manufacturing of (single mode) Vertical-Cavity Surface-Emitting Lasers or in the fabrication of more recently-demonstrated integrated photonic devices. To facilitate the deployment of VCSELs in their up-rising markets but also to sustain the above-mentioned emerging uses, the shape and size of the optical/electrical apertures resulting from the selective lateral oxidation of buried layers of aluminium-containing III-V semiconductors need to be controlled with an ever-increasing accuracy and reliability. In this presentation, we will review the recent experimental investigations and model developments we have carried out to analyse and describe in detail this oxidation process. In particular, we will show that its degree of anisotropy depends on the oxidation process conditions and that the detrimental shape distortion induced by this anisotropy may be mitigated by a careful design of the etched mesas used to enable the oxidation of the buried layers.

Gerardo Castañón
Efficient designs of splitter/combiner silicon photonics devices
A. F. Martínez-Herrera and G. A. Castañón
Tecnológico de Monterrey, Mexico
Currently, silicon photonics has emerged as feasible solution to develop novel and efficient devices, to substitute those electronic components in telecommunications and computer devices that have reached their physical limits in terms of area, energy, speed and bandwidth, which impact in the total cost of manufacturing. In this paper, a simulation performance evaluation of two small splitters/combiners are presented, where their corresponding size is about 1.55 μm and 1.38 μm with a 450 nm of waveguide width, by taking care about the manufacturing rules. The performance of these devices are compared against to a modified version of one of the smallest splitters/combiners that exist nowadays in the literature. Keywords: Splitter, combiner, compact design, silicon photonics.

Victor Dolores-Calzadilla
RF interconnects for high-speed and dense photonic integrated circuits developed through open innovation
V. Dolores-Calzadilla et al., Eindhoven University of Technology, The Netherlands
We present the open innovation development of low loss radio-frequency interconnects for a generic InP photonic integrated platform. The proposed interconnects add a degree of freedom for the metal routing, thereby enabling both high speed and denser photonic integrated circuits (PICs). As the fabrication is carried out by post-processing, it can be integrated in a flexible way within the manufacturing process of PICs.

Sébastien Cueff
Vanadium oxide based waveguide modulator integrated on silicon
J. John^{1, 2}, R. Orobtchouk², P. Rojo-Romeo¹, B. Vilquin¹, Zhen Zhang³, S. Ramanathan³, and S. Cueff^1
1Université de Lyon, Ecole Centrale de Lyon, Institut des Nanotechnologies de Lyon, CNRS UMR5270, Ecully, France
²Université de Lyon, INSA de Lyon, Institut des Nanotechnologies de Lyon, CNRS UMR5270, Villeurbanne, France
³School of Materials Engineering, Purdue University, West Lafayette, Indiana, USA
Silicon photonics is now a mature field of research with efficient passive building blocks such as waveguides, routers and modulators. Silicon, as a material though, is not the best material for light emission and electro-optical modulation functionalities. To circumvent those limitations, researchers integrate heterogeneous materials such as for example III-V semiconductors, rare-earth-doped oxides and ferroelectric oxides on silicon. In this communication, we present a simple and innovative straight waveguide modulator design based on the phase change properties of Vanadium dioxide (VO₂). VO₂ is a strongly correlated material with unique insulator-to-metal transition (IMT) property. This IMT is accompanied by a structural modification as well as an extremely large modulation of the refractive index in the near-infrared range. We leverage this strong optical tunability in hybrid Silicon/VO₂ waveguides for optical modulation. Specifically, by spatially separating the modulator from the bus waveguide, we both exploit the changes in refractive index and extinction coefficients to maximize modulation as well as minimize transmission loss. We will show how our design enable compact and efficient devices that can be readily integrated on standard Silicon photonics platform. We further discuss on the latest experimental results, expected performances compared to the state-of-the-art and future devices.

John Donegan
Athermal operation of high-order slotted lasers for communications applications
M. J. Wallace, R. McKenna, G. Jain, F. Bello, D. McCloskey, and J. F. Donegan
School of Physics and CRANN, Trinity College Dublin, Ireland
We present results on athermal operation of slotted lasers in which the same laser wavelength is maintained even as the temperature is changed. Two distinct athermal bias current procedures based on thermal tuning are demonstrated for a low-cost, monolithic, three section slotted single mode laser, achieving mode-hop free wavelength stability of ± 0.04 nm / 5 GHz over a temperature range of 8–47 °C. A greater range can be obtained at the cost of mode hops during operation. This is the first time that athermal performance has been demonstrated for a three-section slotted laser with simple fabrication, and is well within the 50 GHz grid spacing specified for DWDM systems. This performance is similar to experiments on more complex DS-DBR lasers, indicating that strong athermal performance can be achieved using our lower-cost three section devices. An analytical model and thermoreflectance measurements will be described with further insight into the operation of multi-section lasers and lay the foundation for an accurate predictive tool for optimising such devices for athermal operation.

Maria Rute Ferreira André
Multifunctional materials for integrated optics with enhanced and tunable optical properties
A. R. N. Bastos¹, L. Fu¹, P. S. André², and R. A. S. Ferreira^1
1Physics Department and CICECO - Aveiro Institute of Materials, University of Aveiro, Portugal
²Department of Electronics, Telecommunications and Informatics, Instituto de Telecomunicações, University of Aveiro, Portugal
Featuring applications on thermo-optic devices, functional organic-inorganic hybrids (tri-ureasils) were processed as waveguides (planar and channel). The waveguides show a refractive index value (1.496±0.001 at 1550 nm) similar to the one of optical fibres, and low attenuation coefficient (1.3±0.1 dB/cm). The refractive index dependence on the temperature was studied, yielding a thermo-optic coefficient value of (−3.5±0.1)×10^-4 °C^-1, which is a high value compared to other polymers and hybrid materials, showing the potential of the proposed material to integrate thermo-optic devices with controllable optical features, easy processing and a cost-effective approach to cope with the requirements of the next generation of optical access networks.

Sonia García-Blanco
Rare-earth ion doped Al₂O₃ on Si₃N₄ platform for on-chip amplifiers and lasers
M. de Goede, L. Chang, J. Mu, C. van Emmerik, M. Dijkstra, and S. M. García-Blanco
Optical Sciences Group, MESA+ Institute for Nanotechnology, University of Twente, The Netherlands
In this paper, the integration of rare-earth ion doped Al₂O₃ on the passive Si₃N₄ waveguide platform will be described in detail. On-chip amplifiers with more than 15 dB/cm net gain as well as narrow linewidth (<250 kHz) microring lasers in this platform will be reported. These devices were utilized as optical biosensors for the detection of biomarkers in undiluted urine, with a limit of detection of ~0.3 nM for the S100A4 protein, which is related to human tumor development.

Olivier Gauthier-Lafaye
Cavity resonator integrated filter (CRIGF) based external cavity laser in a butterfly package
A. Monmayrant¹, L. Ferrières², V. Lecocq², E. Feuillet², S. Denet², O. Gauthier-Lafaye¹, and B. Faure^3
1LAAS-CNRS, Université de Toulouse, France
²INNOPTICS,  Institut d’Optique d’Aquitaine, Talence, France
³CNES, Toulouse, France
Cavity Resonator Grating Filters are narrowband reflective spectral filters that exhibit high efficiency and high angular acceptance, with large optical alignment tolerances. We show that an external cavity diode laser setup with single mode emission can be integrated in a medium size butterfly package using these filters.

Peter Horak
Tilted Bragg gratings as an efficient platform for integrated multimode interference devices
P. Horak, M. J. Weisen, J. C. Gates, C. B. E. Gawith, and P. G. R. Smith
Optoelectronics Research Centre, University of Southampton, UK
We have recently developed and experimentally demonstrated the technology of tilted Bragg gratings in integrated optical waveguides to achieve polarisation selective coupling between parallel waveguides. Here I will review our ideas, designs and simulations for novel devices based on this platform. Multimode devices, tailored phase matching, and methods for significantly improved coupling efficiencies will be discussed that will be of interest for applications in quantum information processing and multimode optical telecommunication.

Hamza Kurt
Inverse design of integrated photonic structures
Y. A. Yilmaz, A. M. Alpkilic, M. Tutgun, D. Yilmaz, I. A. Atalay, A. Yeltik, and H. Kurt
Department of Electrical and Electronics Engineering, TOBB University of Economics and Technology, Ankara, Turkey
Designs of photonic devices have been mainly based on intuitive and brute-force approach. However, there has been increasing demand in photonics to obtain high device performance and improved functionalities along with small footprints. Among the different algorithms developed so far, objective-first inverse-design algorithm is one of the greatly utilized method. In the present work, we apply inverse design algorithm to investigate efficient and compact 1xN (1x2, 1x4, 1x6) wavelength de-multiplexers for use at telecommunications wavelengths. Besides, we study different photonic structures such as nano-beam cavity, optical filters and solar cell. Contrary to the forward design method, inverse design approach provides functional and compact photonic devices and it opens new avenues in exploiting the full space of practical structures.

Pascal Landais
Characterisation of a novel InP photonic integrated circuits for direct modulation applications
M. Hammad¹, G. Jain¹, A. Kaszubowska-Anandarajah², P. Anandarajah¹, and P. Landais^1
1School of Electronic Engineering, Dublin City University, Ireland
²CONNECT Research Centre, Trinity College Dublin, Ireland
In this paper, we present two InP based photonic integrated devices used for direct modulation applications. These devices consist of two lasers which can be used in a master-slave configuration. A detailed study on the interaction between the different sections of the PICs and their impact on the static and dynamic characteristics is given.

Sylwester Latkowski
Open standard test framework for photonic integrated circuits
S. Latkowski, D. Pustakhod, M. Chatzimichailidis, X. Leijtens, and K. Williams
Institute for Photonic Integration, Eindhoven University of Technology, Eindhoven, The Netherlands
Test, assembly and packaging processes substantially contribute to the overall production cost of photonic integrated circuits. Implementation of test processes across the full production chain is critical in order to deliver statistically significant data sets. These will allow for optimization of the fabrication process widows, early known-good-die selection, improved models in design tools and lead to improved yield, reduced cost and scalability which will open a path to volume production. Progress on developments of open access test infrastructure at our laboratories and open standard test framework will be presented.

Chonghuai Ma
All-optical readout for integrated photonic reservoir computing
Chonghuai Ma¹, S. Sackesyn¹, J. Dambre², and P. Bienstman^1
1Photonics Research group, UGent – imec, Gent, Belgium
²IDLab, UGent – imec, Gent, Belgium
Photonic neuromorphic computing has gained a lot of attention for its strong potential to deliver machine learning computation capability at high bitrates (>32 Gbps) with very low energy consumption. Reservoir computing is one of the strong candidates that delivers a huge advantage on a real hardware implementation. However one of the challenges is that current readout systems are the bottleneck of the high-speed link involving heavy power consumption from optoelectrical conversions. In this paper, we present our design of an integrated all-optical readout system that overcomes the challenges with optical weighting elements, which works at 32 Gbps and can deliver computation capability on-chip with one final readout signal channel. Furthermore, this paper addresses the problem of some non-volatile optical weighting elements having limited weighting resolutions and drifting noise with our proposed method in the system training phase. As a result, the readout system can still perform closely at an ultra-low resolution (3 bit) with noise involved compared to using full resolution weighting elements.

Leif Oxenløwe
Towards ultra-efficient frequency comb generation in AlGaAs-on-insulator
A. N. Kamel, E. Stassen, Yi Zheng, Chanju Kim, Minhao Pu, L. K. Oxenløwe, and K. Yvind
CoE SPOC, DTU Fotonik, Technical University of Denmark, Lyngby, Denmark
Aluminum gallium arsenide (AlGaAs) is an attractive material for nonlinear applications due to its high Kerr nonlinearity and low nonlinear loss. In the AlGaAs-on-insulator chip-integrated platform, high nonlinearity is combined with tight optical mode confinement to produce efficient devices for four-wave mixing and frequency comb generation. We report on our progress in fabricating low loss AlGaAs-on-insulator waveguides and the challenges imposed by interface state absorption.

Joan Manel Ramirez
Hybrid III-V on Si photonic integrated circuits for high-speed optical communications: Roadmap and perspectives
J. Manel Ramirez¹, H. Elfaiki¹, T. Verolet¹, D. Néel¹, K. Hassan², C. Jany², S. Malhouitre², A. Gallet¹, A. Shen¹, C. Caillaud¹, D. Make¹, H. Gariah¹, and M. Achouche^1
1III-V lab, a joint fab from Nokia, Thales and CEA, Palaiseau, France
²CEA LETI, Minatec, Grenoble, France
In line with the technological revolution of our hyper connected society, there is a strong demand to improve the current data transmission systems to enable new communication channels which are faster, more secure and more energetically efficient. It is then necessary to develop new optical transceivers (transmitters and receptors) able to perform at high operation speeds (> 10 Tb/s) using a low cost technology. In this context, Silicon Photonics has recently raised as a promising and elegant solution able to fulfil all these requirements owing to the abundance on earth of its prime material, silicon (Si), and the maturity of the CMOS technology. Despite all these benefits, Si is an indirect band-gap material and therefore is known to have poor light emitting properties, hence providing a strong constraint when willing to develop Si-based light emitting sources. Nevertheless, other approaches are suitable, notably the hybrid integration of III-V semiconductor materials on Si platforms. In this regard, the III-V lab has demonstrated high performance hybrid III-V lasers integrated on Si by using molecular bonding. These laser diodes present wide lasing wavelength tunability that spans over 80 nm, with a central wavelength at either the O-band (λ = 1260 – 1360 nm), the C-band (λ = 1530 – 1565 nm) or the L-band (λ = 1565 – 1625 nm), depending on the system demands. In this paper, we will review the most recent advances of the III-V lab on hybrid III-V on Si integrated tunable lasers and their crucial role on fast optical communication transceivers for datacom architectures (4x25 Gb/s) as well as for long-haul telecommunications using in-phase and quadrature modulation schemes.

Elena Pinilla-Cienfuegos
New molecular-based materials for enabling electro-optical bistability in the silicon photonics platform
E. Pinilla-Cienfuegos¹, A. Brimont¹, I. Olivares¹, J. Parra¹, R. Sanchis-Gual², R. Torres-Cavanillas², M. Giménez-Marqués², E. Coronado², and P. Sanchis^1
1Nanophotonics Technology Center, Universitat Politècnica de València, Spain
²Instituto de Ciencia Molecular (ICMol), Universidad de Valencia, Paterna, Spain
Electro-optical bistability is a functionality which can be crucial for a wide range of applications as it can enable non-volatile and ultra-low power switching performance. We propose the integration of a molecular-based material presenting a Spin Crossover (SCO) effect in the silicon platform to accomplish for the first time this challenge. The SCO Crossover phenomenon involves a switching process between two molecular spin states. This spin transition comes along with an abrupt change in the electrical and optical properties (conductance, dielectric constant and refractive index) that can be switched by different external stimuli such as a variation of temperature or light irradiation. The SCO material can be synthetized as nanoparticles so that it can be easily integrated in the silicon platform and allows switching at room temperature.

Alejandro Sánchez Postigo
Suspended silicon integrated platform for the long-wavelength mid-infrared band
A. Sánchez-Postigo¹, G. Wangüemert-Pérez¹, J. Soler Penadés², A. Ortega-Moñux¹, M. Nedeljkovic², R. Halir¹, F. El Mokhtari Mimum¹, Zhibo Qu², A. Z. Khokhar², A. Osman², Wei Cao², C. G. Littlejohns², G. Z. Mashanovich², P. Cheben³, and Í. Molina-Fernández^1
1Universidad de Málaga, Dpto. Ingeniería de Comunicaciones, ETSI Telecomunicación, Málaga, Spain
²Optoelectronics Research Centre, University of Southampton, UK
³National Research Council Canada, Ottawa, Canada
The atmospheric-transmission window and the fingerprint region of many substances overlaps with the long-wave infrared band. This has enabled the emergence of a new path for photonic integrated circuits, which could exploit the potential applications of this wavelength range, including chemical and bio sensing.  In this work we review our latest advances in the suspended silicon platform with subwavelength grating lateral cladding at 7.7-µm wavelength. Suspended waveguides only require one lithographic etch step and can be specifically designed to maximize sensitivity when used as sensors. Waveguides with propagation loss of 3.1±0.3 dB/cm are demonstrated, as well as bends with less than 0.1 dB/bend. Suspended waveguides based on shifted Bragg grating lateral cladding are also reported, with propagation loss of 5.1±0.6 dB/cm. These results prepare the ground for the development of a platform capable of covering the entire mid-infrared band.

Dana Seyringer
Compact and high-resolution 256-channel silicon nitride based AWG spectrometer for OCT on a chip
D. Seyringer¹, M. Sagmeister², A. Maese-Novo³, M. Eggeling³, E. Rank⁴, J. Edlinger¹, P. Muellner³, R. Hainberger³, W. Drexler⁴, J. Kraft², G. Koppitsch², G. Meinhardt², M. Vlaskovic², and H. Zimmermann^5
1Research Centre for Microtechnology, Vorarlberg University of Applied Sciences, Dornbirn, Austria
²ams AG, Premstätten, Austria
³AIT Austrian Institute of Technology GmbH, Wien, Austria
⁴Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Austria
⁵Institute of Electrodynamics, Microwave and Circuit Engineering, TU Wien, Austria
We present the design, simulation and technological verification of a compact high-resolution 256-channel, 42-GHz silicon nitride based AWG-spectrometer. The spectrometer was designed for TM-polarized light with a central wavelength of 850 nm, applying our proprietary “AWG-Parameters” tool. This design is based on a previous study of various AWG designs (8-channel, 100-GHz; 20-channel, 50-GHz; 40-channel, 50-GHz, 80-channel, 50-GHz and 160-channel, 50-GHz AWGs), which were all technologically verified. The spectrometer features small size and high resolution. It is integrated on an OCT chip using standard CMOS processes. The spectral domain optical coherence tomography system is developed to operate in a wavelength range of 800 nm to 900 nm, having 0.1 nm resolution.

Jordi Soler Penades
Suspended germanium waveguide for infrared wavelengths
J. Soler Penades¹, A. Sanchez-Postigo², M. Nedeljkovic¹, G. Wangüemert-Perez², A. Ortega-Moñux², R. Halir², A. Z. Khokhar¹, A. Osman¹, I. Molina-Fernandez², and G. Z. Mashanovich^1
1Optoelectronics Research Centre, University of Southampton, UK
²Dept. de Ingeniería de Comunicaciones, ETSI Telecomunicación, Universidad de Málaga, Spain
Silicon-on-insulator (SOI) is the dominant platform in near-infrared silicon photonics. However, the high absorption of SiO₂ at wavelengths above 4 µm limits the range at which this material can be used in the mid-infrared (2-20 µm). In this work we review our recent work on suspended devices, building on our previous work based on suspended silicon devices with subwavelength grating (SWG) lateral cladding at 3.8 µm and our more recent results at 7.7 µm. This platform uses the well-known fabrication techniques of SOI, only requires a single lithographic etch step and it allows the use of the whole transparency range of the waveguide core material. Due to this it could be a good candidate for sensing applications since the design covers a very large wavelength range and, as the bottom cladding of the waveguide is air, the waveguide can be designed so that the mode is squeezed to increase the evanescent field proportion and therefore the interaction with a surrounding analyte.

Isaac Suárez
Amplified spontaneous emission in thin films of CsPbX₃ perovskite nanocrystals
J. Navarro-Arenas¹, A. F. Gualdrón-Reyes², V. S. Chirvony¹, I. Mora-Seró², J. Martínez-Pastor¹, and I. Suárez^1,3
1Instituto de Ciencia de Materiales (ICMUV), Universidad de Valencia, Paterna, Spain
²Institute of Advanced Materials (INAM), Universitat Jaume I, Castelló, Spain
³ School of Telecommunications Engineering, Electronics Area, Universidad Rey Juan Carlos, Fuenlabrada, Spain
During the last years, Metal Halide Perovskites (MHPs) have attracted special attention as an efficient conversion films for photovoltaics, or excellent gain media to construct optical sources. In spite of the fact that most of the works have been focussed on CH₃NH₃PbX₃ (X=Cl, Br, I) polycrystalline thin films, MHP can be also synthesized as colloidal nanocrystals. In particular, caesium lead halide perovskite CsPbX₃ nanocrystals (NCs) revealed extraordinary properties for optoelectronics. With a high quantum yield of emission (>90%) at room temperature and linewidths less than 100 meV, CsPbX₃ NCs have demonstrated favourable characteristics for active photonics. Indeed, thin films of CsPbBr₃ optically pumped by femtosecond pulses resulted in amplified spontaneous emission (ASE) with thresholds less than 10 μJ/cm2 or lasers with linewidths narrower than 0.2 nm. A further improvement of these results towards the performances demonstrated by their counterpart polycrystalline films, however, requires a reduction of  different nonradiative recombination channels restricting the ASE. In this work, films of CsPbBr₃ NCs are properly optimized to enhance the generation of photoluminescence (PL), and with it the optical gain. Indeed, the dependence of PL on temperature reveals the activation energies of nonradiative traps higher than 10 meV. Consequently, these films demonstrate ASE thresholds less than 5 μJ/cm²  at cryogenic temperatures under nanosecond excitation. These preliminary results pave the road towards a CsPbBr₃ active photonics technology.

Dimitris Tsiokos
Plasmonic waveguides co-integrated with Si₃N₄ waveguide platform for integrated biosensors
A. Manolis¹, G. Dabos¹, N. Pleros¹, E. Chatzianagnostou¹, D. Ketzaki¹, L. Markey², J.C. Weeber², A. Dereux², A.L. Giesecke³, C. Porschatis³, B. Chmielak³, P. J. Cegielski³, S. Suckow³, and D. Tsiokos^1,4
1Center for Interdisciplinary Research and Innovation, Aristotle University of Thessaloniki, Greece
²Laboratoire Interdisciplinaire Carnot de Bourgogne, CNRS-Université de Bourgogne, France
³AMO GmbH, Advanced Microelectronic Center Aachen (AMICA), Germany
⁴bialoom Ltd, Nicosia, Cyprus
Integration of plasmonic waveguides with low-loss photonic platforms have attracted research efforts as the means to benefit from the extra-ordinary features of plasmonics while enhancing the functional portfolio of Photonic Integrated Circuits (PICs). In this work, we review a technology platform that integrates water cladded plasmonic waveguides integrated in a low-loss Si₃N₄ photonic platform, targeting biosensing applications. Results obtained experimentally and numerically will be presented with respect to propagation losses, interface coupling loss and accumulated phase change per unit length, showing how Surface Plasmon Polariton (SPP) waveguides can be effectively combined with photonic components in order to demonstrate low-cost and ultra-sensitive optical biosensors.

Shumin Wang
Integration of wafer scale III-V on Si for optoelectronics
Shumin Wang^1,2
1Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, China
²Department of Microtechnology and Nanoscience, Chalmers University of Technology, Goteborg, Sweden
In this invited talk, we will present some recent progresses on wafer scale integration of GaAs, InP, InAs and GaSb thin film templates on Si substrates using innovative smart cutting by ion implantation, wafer bonding, splitting and surface treatment. High quality thin film templates (less than 0.5 µm thick) with a surface roughness less than 1 nm and a line-width of less than 100 seconds in X-ray diffraction are achieved. Quantum well structures epitaxially grown on such templates by molecular beam epitaxy reveal comparable photoluminescence properties with those grown on commercial III-V substrates.

Quantum Photonics invited presentations:

Daniele Bajoni
A source of heralded single photon using high quality factor silicon ring resonators
F. A. Sabattoli¹, H. El Dirani², F. Garrisi¹, S. Sam⁵, C. Petit-Etienne³, J.M. Hartmann², E. Pargon³, C. Monat⁴, M. Liscidini¹, C. Sciancalepore², M. Galli¹, and D. Bajoni^5
1Dipartimento di Fisica, Università di Pavia, Italy
²Université Grenoble Alpes, CEA-LETI Minatec, France
³LTM, CNRS, Université Grenoble Alpes, France
⁴Institut des Nanotechnologies de Lyon, Ecully, France
⁵Dipartimento di Ingegneria Industriale e dell’Informazione, Università di Pavia, Italy
We show generation of quantum states of light using high quality factor silicon ring resonators. Quality factors exceeding 105 are obtained via atomic-scale smoothening of the waveguides sidewalls roughness thanks to high temperature hydrogen annealing. The high quality factors yield emission of photon pairs with high rate, and we report heralding of single photons generated in our rings with values of g(2)(0) as low as 0:021 ± 0.003.

Daryl Beggs
Angled cage etching for integrated quantum photonics in GaN
D. M. Beggs, R. A. Taylor, B. Humphreys, G. P. Gough, and A. J. Bennett
University of Cardiff, UK
We have developed a single step angled etching technique using a Faraday cage to create free-standing gallium nitride quantum photonic devices. GaN has many advantages as a photonic material, but the fabrication process is complicated as no undercutting is available. Complex and bespoke fabrication procedures are needed for creation of the high-index contrast structures. Here, we aim to eliminate these additional processing steps by the angled etching of the substrate to undercut waveguides and devices, giving the possibility of the tight confinement needed for enhancement of the light-matter interaction. To create the angled etch, we use ICP etching with an angled Faraday cage over the sample, which directs the impacting ions along field lines perpendicular to the cage and towards the substrate at a steep angle. The angled etching can create high contrast waveguides without the need for additional undercutting steps, which are difficult to achieve in GaN.

Wolfgang Elsäßer
Ghost metrology with classical light – The story continues: Ghost spectroscopy and ghost polarimetry
W. Elsäßer, Institute of Applied Physics, Technische Universität Darmstadt, Germany
Ghost metrology is a measurement modality exploiting correlation of photons. We demonstrate that amplified spontaneous emission light emitted both by a broad-band semiconductor-based superluminescent diode and an erbium-doped fibre amplifier (EDFA) exhibit in fact photon correlations in the spirit of the Hanbury-Brown & Twiss (HBT) experiment, however now in the spectral domain. We then apply these spectral photon correlations within a proof-of-principal ghost spectroscopy experiment at an absorption band of trichloromethane (chloroform) at 1214 nm and at 1533 nm at acetylene (C₂H₂) reproducing the characteristic absorption features. This ghost-spectroscopy work fills the gap of a hitherto missing analogy between the spatial and the spectral domain in classical ghost modalities. Finally, by exploiting polarization correlations of light from an EDFA we succeed in reconstructing a hidden, camouflaged polarization in a ghost polarimetry experiment in close analogy to ghost imaging and ghost spectroscopy. Via these results, we expect contributing towards a broader dissemination of correlated photon ghost modalities, hence paving the way towards more applications which exploit the favourable advantages.

Mark Fox
Chiral quantum photonics in semiconductor nano-photonic waveguides
A. M. Fox, Department of Physics and Astronomy, University of Sheffield, UK
In this presentation, I will review progress towards implementing chiral quantum photonics in GaAs nano-photonic waveguides. The chiral coupling occurs when a semiconductor quantum dot (QD) is positioned close to a C-Point (chiral point) of the waveguide. The off-centre positioning of the QD breaks the inversion symmetry, and results in a strong dependence of the propagation direction on the circular polarization of the optical mode, with spin up and spin down exciton spins coupling to the left and right propagation directions respectively. In previous work we demonstrated incoherent, spin-dependent directional photoluminescence and initialization using non-resonant and quasi-resonant excitation [1, 2]. In this presentation, I will present results for coherent, resonant excitation in transmission and reflection geometries [3]. Numerical simulations for a quantum two-level system are able to reproduce the observed behaviour, and indicate that the spin-dependent phase shift in transmission is around 0.1p in the current devices. Strategies to increase the phase shift towards the ideal value of p required to implement chip-based spin networks will be discussed.
[1] Coles, R.J. et al., Nature Communications 7, 11183 (2016).
[2] Coles, R.J. et al., Phys. Rev. B. 95, 121401(R) (2017).
[3] Hurst, D.L. et al., Nano Letters 18, 5475 (2018).

Alessandro Gaggero
Amplitude multiplexing readout of an integrated autocorrelator
A. Gaggero¹, F. Martini¹, F.Mattioli¹, R. Cernansky², A. Politi², F. Chiarello¹, and R. Leoni^1
1Istituto di Fotonica e Nanotecnologie – CNR, Roma, Italy
²Department of Physics and Astronomy, University of Southampton, UK
The realization of large-scale photonic circuits for quantum optics experiments requires an increasing number of integrated detectors. Superconducting nanowire single photon detectors (SNSPDs) can be easily integrated on chip to efficiently detect the light propagating inside waveguides. In this paper, we propose and implement a novel amplitude-multiplexing scheme allowing the efficient readout of several SNSPDs with only one coaxial cable.

Eli Kapon
Integrated quantum photonics with tailored potential quantum dots and photonics crystal structures
E. Kapon, Laboratory of Physics of Nanostructures, Ecole Polytechnique Fédérale de Lausanne, Switzerland

Marco Liscidini
Generation of photon pairs in topologically protected guided modes
N. Bergamasco and M. Liscidini
Dipartimento di Fisica, University of Pavia, Italy
Recent works suggest that the propagation of quantum states can be protected by exploiting topology in silicon integrated waveguide arrays. More recently, it has been suggested that topologically protected guided modes may also play an important role in the generation of photon pairs via spontaneous four-wave mixing SFWM, for path correlations of the generated photons in these systems seem to be robust with respect to fabrication imperfections. In this work we investigate the effects of the disorder on SFWM efficiency and quantum correlations in topologically protected guided modes in waveguide arrays.

Khaled Mnaymneh
From conventional photonic circuitry to quantum photonic circuitry: All at the drop of a nanowire
K. Mnaymneh, D. Dalacu, D. B. Northeast, J. McKee, J. Lapointe, S. Haffouz, P. J. Poole, G. C. Aers, and R. L. Williams
National Research Council Canada, Ottawa, Canada
Field-ready quantum technologies require highly efficient, highly robust, quantum sources in order to manifest useful next-generation applications based upon quantum coherence and entanglement. In this talk, we present a pick-and-place technique for selecting and transferring individual InP tapered nanowires, each containing a single InAs quantum dot, and placing them onto silicon-based optical waveguides. The tapered geometry of the nanowire enables highly efficient evanescent coupling of single-photons from the dot into the waveguides. This coupling can also be used to optically pump the dot from the same waveguide it emits into, enabling a completely integrated fiber-coupled plug-and-play solution ready for field applications requiring a source of bright, on-demand single photons.

Roberto Morandotti
Kerr combs and telecommunications components for the generation and high-dimensional quantum processing of d-level cluster states
P. Roztocki¹, C. Reimer^1,2, S. Sciara^1,3, M. Islam¹, L. Romero Cortés¹, Yanbing Zhang¹, B. Fischer¹, S. Loranger^4,5, R. Kashyap^4,6, A. Cino³, Sai T. Chu⁷, B. E. Little⁸, D. J. Moss⁹, L. Caspani¹⁰, W. J. Munro^11,12, J. Azaña¹, M. Kues^1,13, and R. Morandotti^1,14,15
1Institut National de la Recherche Scientifique (INRS-EMT), Varennes, Canada
²HyperLight Corporation, Cambridge, MA, USA
³Department of Energy, Information Engineering and Mathematical Models, University of Palermo, Italy
⁴Engineering Physics Department, Polytechnique Montreal, Canada
⁵Max Planck Institute for the Science of Light, Erlangen, Germany
⁶Electrical Engineering Department, Polytechnique Montreal, Canada
⁷Department of Physics and Material Science, City University of Hong Kong, China
⁸State Key Laboratory of Transient Optics, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Science, Xi’an, China
⁹Centre for Micro Photonics, Swinburne University of Technology, Hawthorn, Australia
¹⁰Institute of Photonics, Department of Physics, University of Strathclyde, Glasgow, UK
¹¹NTT Basic Research Laboratories and NTT Research Center for Theoretical Quantum Physics, NTT Corporation, Kanagawa, Japan
¹²National Institute of Informatics, Tokyo, Japan
¹³School of Engineering, University of Glasgow, UK
¹⁴Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu, China
¹⁵ITMO University, St Petersburg, Russia
Large and complex optical quantum states are a key resource for fundamental science and applications such as quantum communications, information processing, and metrology. In this context, cluster states are a particularly important class because they enable the realization of universal quantum computers by means of the so-called ‘one-way’ scheme, where processing operations are performed through measurements on the state. While two-level (i.e. qubit) cluster states have been realized thus far, further boosting this computational resource by increasing the number of particles comes at the price of significantly reduced coherence time and detection rates, as well as increased sensitivity to noise. In contrast, the realization of d-level (with d>2) cluster states offers the possibility to increase quantum resources without changing the number of particles, enables the implementation of efficient computational protocols, as well as coincides with a reduction in the noise sensitivity of the states. Here, we experimentally realize, characterize, and perform one-way processing operations on three-level, four-partite cluster states formed by two photons in the time and frequency domain. We use of a unique approach based on integrated photonic chips and optical fiber communications components, enabling scalable, deterministic new functionalities.

Peter Mosley
Nonlinear photonics for quantum networks large and small
T. A. Wright, O. Gibson, C. Parry, R. A. Hoggarth, R. J. A. Francis-Jones, and P. J. Mosley
Centre for Photonics and Photonic Materials, Department of Physics, University of Bath, UK
Optical networks offer unique opportunities to realise the potential of quantum technologies across a wide range of scales, from photonic quantum-information-processing chips through to long-haul secure communications. This talk will cover two areas within this spectrum in which work is ongoing at the University of Bath. Firstly we will present results from small-scale fibre networks incorporating active switching to enhance the performance of single-photon sources based on nonlinear photon-pair generation. Secondly we will discuss efforts within the Networked Quantum Information Technology Hub to create a hybrid quantum network of ions linked by photons, incorporating nonlinear frequency conversion for long-distance transmission of quantum information in fibre.

Mikhail Vasilevskiy
Exciton-polaritons in a cylindrical microcavity with an embedded 2D semiconductor layer
J. N. S. Gomes^1,2, C. Trallero-Giner^3,4, N. M. R. Peres^1,2, and M. I. Vasilevskiy^1,2
1Centro de Física, Universidade do Minho, Braga, Portugal
²International Iberian Nanotechnology Laboratory, Braga, Portugal
³Facultad de Física, Universidad de La Habana, Cuba
⁴CLAF – Centro Latino-Americano de Física, Rio de Janeiro, Brasil
Exciton-polariton modes will be discussed, formed by the interaction between excitons in a 2D layer of a transition metal dichalcogenide (TMD) embedded in a cylindrical microcavity and the microcavity photons. Classical electrodynamics provides dispersion relations for the polariton modes, while the quantum-mechanical treatment of a simplified model yields the Hopfield coefficients, measuring the degree of exciton-photon mixing in the coupled modes. The density of states (DOS) and its projection onto the photonic subspace are calculated taking monolayer MoS2 embedded in a silica cylinder as an example. The calculated results demonstrate a strong enhancement of the local DOS and spontaneous emission rate of a quantum emitter placed in the microcavity (Purcell effect), caused by the presence of the 2D layer.

Quantum Communications invited presentations:

Hercules Avramopoulos
Coexistence of discrete-variable QKD with WDM classical signals in the C-band for fiber access environments
D. Zavitsanos¹, G. Giannoulis¹, A. Raptakis¹, C. Papananos¹, F. Setaki², E. Theodoropoulou², G. Lyberopoulos², Ch. Kouloumentas^1,3, H. Avramopoulos^1
1National Technical University of Athens, Greece
²COSMOTE Kinites Tilepikoinonies A.E., Athens, Greece
³Optagon Photonics, Athens, Greece
In this paper, a coexistence scheme between a Discrete-Variable Quantum Key Distribution (DV-QKD) and four bidirectional classical channels in a Passive Optical Network (PON) topology is theoretically investigated. The study aims to explore the imposed limitations considering the coexistence of weak quantum channels with realistic traffic flows of classical streams through shared fiber infrastructures. Based on a ‘plug and play’ phase coding DV-QKD implementation, we conducted numerical simulations of the QBER and the secure key rate for fiber distances up to 10 km. The reported results suggest that in a fixed C-band grid, the spectral isolation between classical and quantum channels is essential at dense grids. By removing the leakage noise through stronger spectral isolation, the photons linked with the Raman scattering become the dominant noise source, since this mechanism covers an ultra-broadband window and gets stronger as the propagation distance increases.

David Bacco
High-dimensional quantum communication using space encoding
D. Bacco, D. Cozzolino, B. Da Lio, Yunhong Ding, K. Ingerslev, M. Galili, K. Rottwitt, S. Ramachandran, and L. K. Oxenløwe
CoE SPOC, DTU Fotonik, Technical University of Denmark, Lyngby, Denmark
Quantum communication (QC) represents a key enabler for many quantum applications. However, low information rates and short propagation distances, limit the development of this field and its practical applications. High-dimensional (Hi-D) QC can address these challenges enhancing the information rate and the systems error tolerance. We report our recent results on Hi-D quantum communication where we prove the capability of preparing, manipulating, transmitting and measuring Hi-D quantum states through multi-core and multimode fiber.

Konrad Banaszek
Beating the standard quantum limit for binary constellations in the presence of phase noise
L. Kunz¹, M. T. DiMario², F. E. Becerra², and K. Banaszek^1
1Centre for Quantum Optical Technologies and Faculty of Physics, University of Warsaw, Poland
²Center for Quantum Information and Control, Department of Physics and Astronomy, University of New Mexico, Albuquerque, USA
Unconventional receivers enable reduction of error rates in optical communication systems below the standard quantum limit (SQL) by implementing discrimination strategies for constellation symbols that go beyond the canonical measurement of the information-carrying quantity such as the intensity or a quadrature the electromagnetic field. An example of such a strategy is presented here for average-power constrained binary constellations propagating through a phase noise channel. The receiver, implementing a coherent displacement in the complex amplitude plane followed by photon number resolved detection, can be viewed as an interpolation between direct detection and homodyne detection.

Marcos Curty
Towards quantum key distribution with implementation security
M. Curty, Escuela de Ingeniería de Telecomunicación, Dept. of Signal Theory and Communications, University of Vigo, Spain
Quantum key distribution (QKD) is surely the most mature application of the future global quantum internet. In theory, it provides information-theoretically secure communications based on the laws of quantum physics. In practice, however, current security proofs of QKD rely on assumptions which are not fulfilled by the real setups, and thus the security of QKD implementations is seriously threatened by quantum hacking. This includes, for instance, the assumption that the legitimate users of the system have a precise mathematical description of the behaviour of their apparatuses, that all quantum devices and classical post-processing units are honest and follow the prescriptions of the protocol, and that the systems are located in protected labs which prevent that unwanted information is leaked to the channel. Here, we present recent results to significantly relax these unrealistic and hardly feasible requirements to achieve practical QKD with implementation security.

Virginia D’Auria
Chip-based compact squeezing experiment at a telecom wavelength
F. Mondain¹, T. Lunghi¹, A. Zavatta^2,3, É. Gouzien¹, F. Doutre¹, M. de Micheli¹, S. Tanzilli¹, and V. D’Auria^1
1Université Côte d’Azur, Institut de Physique de Nice (INPHYNI), CNRS UMR 7010, Nice, France
²Istituto Nazionale di Ottica (INO-CNR), Firenze, Italy
³LENS and Department of Physics, Universitá di Firenze, Italy
In the context of quantum communication and technologies squeezed states of light represent a crucial resource. Nevertheless, their generation and detection usually demand complex bulk systems, hardly compatible with out-of-the-laboratory realizations. In view of future practical applications, we present a compact and easy-to-use set-up exploiting the association of commercial plug-and-play fibre components and integrated optics on lithium niobate for the generation and detection of squeezed light at a telecom wavelength. Light exhibits a reduced quantum noise of -2.00±0.05 dB below the shot-noise level in a single-pass configuration.

Eleni Diamanti
Demonstrating quantum advantage in security and efficiency with practical photonic systems
E. Diamanti, CNRS, Sorbonne Université, Paris, France
In this talk, we discuss the current landscape in quantum communication and cryptography, and focus in particular on recent photonic implementations, using encoding in discrete or continuous properties of light, of central quantum network protocols, enabling secret key distribution, verification of entangled resources and transactions of quantum money, with maximal security guarantees. We also describe current challenges in this field and our efforts towards the miniaturization of the developed photonic systems, their integration into telecommunication network infrastructures, including with satellite links, as well as the practical demonstration of novel protocols featuring a quantum advantage in communication efficiency for a wide range of useful tasks in a network environment. These advances enrich the resources and applications of the emerging quantum networks that will play a central role in the context of future quantum-safe communications.

Yunhong Ding
Silicon photonics for quantum communication
Yunhong Ding, D. Bacco, D. Llewellyn, I. Faruque, S. Paesani, M. Galili, A. Liang, K. Rottwitt, M. Thompson, Jianwei Wang, and L. K. Oxenløwe
Department of Photonics Engineering, DTU Fotonik, Technical University of Denmark, Kgs. Lyngby, Denmark
Silicon quantum photonics, capable to integrate large numbers of optical components with CMOS-compatible fabrication technology and reliably control quantum states, is expected to play an critical role of future quantum communications. In this talk, we will introduce our recent results of silicon photonics for quantum communication, including high-dimensional silicon chip-to-chip quantum key distribution, quantum teleportation, on-chip generation of high-dimensional quantum entanglement, and Hong–Ou–Mandel interference between two different III-V/silicon hybrid lasers.

Ivan Djordjevic
Covert communications-based information reconciliation for quantum key distribution protocols
J. Gariano and I. B. Djordjevic
University of Arizona, Department of Electrical and Computer Engineering, Tucson, USA
The rate at which secure key can be generated in a quantum key distribution (QKD) protocol is fundamentally limited by the loss and the quantum bit-error rate (QBER). Increases to the QBER can stem from detector noise, channel noise, or the presence of an eavesdropper, Eve. Eve is capable of obtaining information of the unsecure key by performing an attack on the quantum channel or by listening to all discussions performed via a noiseless public channel. Conventionally a QKD protocol will perform the information reconciliation over the authenticated public channel, revealing the parity bits used to correct for any quantum bit errors. In this invited paper, the possibility of limiting the information revealed to Eve during the information reconciliation is considered. Using a covert communication channel for the transmission of the parity bits, secure key rates are possible at higher QBER. This is demonstrated through the simulation of a polarization based QKD system implementing the BB84 protocol, showing significant improvement of the secure key rates over the conventional QKD protocols.

Sara Ducci
Generation and manipulation of quantum frequency states of light with AlGaAs chips
S. Francesconi¹, G. Maltese¹, F. Appas¹, A. Lemaître², F. Baboux¹, M. Amanti¹, and S. Ducci^1
1Laboratoire Matériaux et Phénomènes Quantiques, Université Paris Diderot, Sorbonne Paris Cité, CNRS-UMR 7162, France
²Centre de Nanosciences et de Nanotechnologies, CNRS/Université Paris Sud, UMR 9001, Marcoussis, France
We present our results on the generation and manipulation of quantum frequency states of light generated with AlGaAs chips. The cavity effects inherent to our devices allows to directly generate quantum frequency combs; moreover, the manipulation of the wavefunction symmetry allows to obtain both bosonic and fermionic behaviors opening the way to a large variety of applications.

Margarida Facão
Strategies of legitimate parties and an eavesdropper for discretely modulated continuous-variables quantum key distribution protocols
M. Facão, V. Ferreira, A. Marques, T. Freitas, and N. A. Silva
Departamento de Física, Universidade de Aveiro, Portugal
Discretely modulated continuous-variables quantum key distribution (CV-QKD) protocols are usually proposed with phase modulated coherent states being sent by Alice and simple homodyne detection on the Bob side and, in the majority of the studies, their security is analyzed assuming that for low photon number the protocols are similar to a Gaussian-modulated CV-QKD. Here we discuss other detection techniques such as double homodyne, simulate classical attacks and find practical strategies for the legitimate parties to reach the security limits predicted by the Gaussian-modulated CV-QKD.

Veronica Fernandez
Enabling QKD under strong turbulence for wireless networks with tilt wavefront correction
P. Arteaga-Díaz, A. Ocampos-Guillén, and V. Fernandez
Group of Cryptology and Information Security, Department of Information and Communication Technologies, Institute of Physical and Information Technologies (ITEFI), Madrid Spain
Wavefront tilt correction is necessary for reducing beam deviations caused by atmospheric turbulence in the receiver of an optical system. This reduction allows decreasing the receiver’s field of view, which in the case of free-space quantum key distribution (QKD), reduces the solar background noise that reaches the detectors, and with this, the quantum bit error rate (QBER). A wavefront tilt correcting system that stabilizes the beam in two different points of the receiver’s optical axis has been developed and characterised, and it is capable of operating under realistic conditions of strong turbulence with almost perfect ideal correction. The reduced area of beam deviations at the focal plane of the receiver after correction enables a reduction of the QBER of more than 80%, which paves the way to free-space quantum key distribution in daylight under strong turbulence.

Hannes Hübel
Flexible entanglement distribution based on WDM and active switching technology
H. Hübel, B. Schrenk, M. Hentschel, and M. Hentschel
AIT Austrian institute of Technology, Wien, Austria
In future, the distribution of single or entangled photons inside optical networks will be a prerequisite for a general roll-out and adoption of quantum communication technologies. In particular, on-demand routing and active wavelength allocation will be needed to meet the demand of complex network architectures. In the last years several attempts have been made, based either on passive optical WDM technology or active switching of channels. Here we present a novel approach whereby we combine spectral slicing of the emission spectrum of SPDC sources together with space-switches to generate a reconfigurable distribution node for entanglement. The increased switching complexity offered by our hybrid solution allows us to realise quantum ROADMs with up to three degrees.

Rupesh Kumar
Full duplex quantum coherent communication
R. Kumar and T. Spiller
Quantum Communications Hub, University of York, UK
High bandwidth requirement for data communication is being met by classical coherent communication using multi-level modulation of amplitude and phase of light. At the quantum signal levels, coherent communication helps to exchange cryptographic keys between two legitimate users and shows higher key exchange throughput compare to single photon based systems. In this work, I will examine the feasibility of full duplex quantum coherent communication, where both the transmitter and the receiver engage in quantum signal recovery as well as secure key generation.

Rui Lin
Embedding quantum key distribution in optical telecommunication system
R. Lin¹, A. Udalcovs², O. Ozolins^1,2, M. Tang³, S. Fu³, S. Popov¹, T. Ferreira da Silva⁴, G. B. Xavier⁵, and J. Chen^1
1School of Engineering Sciences, KTH Royal Institute of Technology, Stockholm, Sweden
²Netoworking and Transmission Laboratory, RISE Research Institute of Sweden AB, Kista, Sweden
³School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, China
⁴National Institute of Metrology, Quality and Technology, Optical Metrology Division, Duque de Caxias - RJ, Brazil
⁵Institutionen för Systemteknik, Linköpings Universitet, Linköping, Sweden
Optical networks plays an extremely important role in our society by serving the global internet. Nevertheless, it is vulnerable to eavesdroppers and attackers from optical-layer. The signals carried in the fiber can be easily accessed by fiber tapping and the services running can be interrupted by harmful signal/noise insertion. Traditional cryptography secures the data delivery based on encryption algorithms in the upper network-layer, which is now facing severe challenges from the eavesdroppers equipped with super computing power, e.g., the potential quantum computer. Securing the information by quantum theory, quantum key distribution (QKD) has the potential to replace the traditional encryption algorithm. Although there are already a few implementation of the QKD, in most of them an individual dark fiber is assigned for the QKD system to operate in a low noise environment, which is too expensive and impractical. Such incompatibility with the existing telecommunication system remains one of the factors that hinder the QKD deployment. In this talk we will discuss the approaches of embedding QKD in optical systems and recent progress.

Diego Lopez
Quantum services architecture in softwarized infrastructures
D. López¹, A. Aguado², C. Abellán³, V. López¹, A. Pastor-Perales¹, F. de la Iglesia¹, and V. Martin^2
1Telefónica Investigación y Desarrollo, Spain
²Center for Computational Simulation, ETSIInf, Universidad Politécnica de Madrid, Spain
³Quside Technologies, Spain
Quantum computing is posing new threats on our security infrastructure. This has triggered a new research field on quantum-safe methods, and those that rely on the application of quantum principles are commonly referred as quantum cryptography. The most mature development in the field of quantum cryptography is called Quantum Key Distribution (QKD). QKD is a key exchange primitive that can replace existing mechanisms that can become obsolete in the near future. Although QKD has reached a high level of maturity, there is still a long path for a mass market implementation. QKD shall overcome issues such as miniaturization, network integration and the reduction of production costs to make the technology affordable. In this direction, we foresee that QKD systems will evolve following the same path as other networking technologies, where systems will run on specific network cards, integrable in commodity chassis. This work describes part of our activity in the EU H2020 project CiViQ in which quantum technologies, as QKD systems or quantum random number generators (QRNG), will become a single network element that we define as Quantum Switch. This allows for quantum resources (keys or random numbers) to be provided as a service, while the different components are integrated to cooperate for providing the most random and secure bit streams. Furthermore, with the purpose of making our proposal closer to current networking technology, this work also proposes an abstraction logic for making our Quantum Switch suitable to become part of software-defined networking (SDN) architectures. The model, fits in the architecture of the SDN quantum node architecture, that is being under standardization by the European Telecommunications Standards Institute. It permits to operate an entire quantum network using a logically centralized SDN controller, and quantum switches to generate and to forward key material and random numbers across the entire network. This scheme, demonstrated for the first time at the Madrid Quantum Network, will allow for a faster and seamless integration of quantum technologies in the telecommunications infrastructure.

Paolo Martelli
Single-SPAD implementation of quantum key distribution
P. Martelli, M. Brunero, A. Fasiello, F. Rossi, A. Tosi, and M. Martinelli
Politecnico di Milano, Italy
A cost-effective implementation of BB84 protocol for QKD, based on the use of a Faraday rotator variable over four states and a single SPAD, is presented.

Vicente Martin
Quantum aware SDN nodes in the Madrid quantum network
V. Martin¹, A. Aguado¹, V. López³, A. Pastor-Perales³, M. Peev⁴, A. Poppe⁴, A. L. Sanz², and P. Salas^2
1Center for Computational Simulation, ETSIInf, Universidad Politécnica de Madrid, Spain
²Center for Computational Simulation, ETSIT, Universidad Politécnica de Madrid, Spain
³Telefónica Investigación y Desarrollo, Spain
⁴Huawei Technologies Duesseldorf, Germany
QKD technology is mature enough to leave the usual single, point to point, link and create a network. Quantum ad hoc networks, where a separate, quantum-only network, is running in parallel to a classical network have been demonstrated in several occasions. Having to, essentially, duplicate the network to have quantum communications is very expensive and, beyond niche use-cases, fully integrated quantum-classical networks is what the industry demands to accept quantum technologies as a serious networking technology, ready for a broad market uptake. Recently we have reported on the successful deployment of the Madrid Quantum Network. This network is novel because it has been the first installed in production sites of a Telecommunications operator and because it is managed through a Software Defined Networking (SDN) structure that integrates classical and quantum channels. The network was running during four months and we could demonstrate several technologies in the integration of quantum and classical networks. Here we report on one of the key components, the Quantum SDN node and its usage in several use cases, in particular to secure the management of the SDN control plane as a critical infrastructure.

Paulo Mateus
On minimal conditions for secure multiparty computations in the quantum setting
M. Lemus^1,2, P. Yadav^1,2, P. Mateus^1,2, N. Paunković^1,2, and A. Souto^2,3,4
1Instituto Superior Técnico ULisboa, Portugal
²Instituto de Telecomunicacoes, Lisboa, Portugal
³Faculdade Ciencias ULisboa, Campo Grande, Lisboa, Portugal
⁴LASIGE, Dep. de Informatica Faculdade Ciências ULisboa, Campo Grande, Lisboa, Portugal
We investigate the requirements to achieve universally composable bit-commitment by relaxing the conditions imposed classically and replacing their role with quantum effects. We discuss how the use of these effects improve the security over classical solutions.

Giuseppe Patera
Quantum temporal imaging
G. Patera¹, D. B. Horoshko^1,2, and M. I. Kolobov^1
1CNRS, UMR 8523 - PhLAM - Physique des Lasers Atomes et Molécules, Univ. Lille, France
²B. I. Stepanov Institute of Physics, NASB, Minsk, Belarus
Temporal imaging is a technique enabling manipulation of optical signals in a manner similar to manipulation of optical images in spatial domain. In this work we generalize the scheme of conventional temporal imaging to quantum temporal imaging viable for non-classical states of light. As an example, we apply our scheme to tempo-rally broadband squeezed light and demonstrate a possibility of its noiseless magnification. In particular, we show that one can magnify by a given factor the coherence time of squeezed light and match it to the response time of the photodetector. This feature opens new possibilities for practical applications of temporally broadband squeezed light in quantum technologies.

Armando Pinto
The impact of fiber random birefringence in polarization-encoded quantum communications
A. N. Pinto, M. F. Ramos, A. C. Santos, N. A. Silva, and N. J. Muga
Universidade de Aveiro, Instituto de Telecomunicações, Aveiro, Portugal
We analyze the impact of fiber random birefringence in realistic quantum communication systems in which information is encoded in single-photon polarization qubits. We present an algorithm to dynamically compensated the polarization random rotations. We assess the algorithm performance considering both the polarization drift dynamics and the QBER threshold.

Andreas Poppe
Simulation of a real-world driven reference QKD-network
A. Poppe¹, M. Gunkel², F. Wissel², P. Schilder², M. Franzke², and M. Peev^1
1Optical and Quantum Communications Laboratory, Munich Research Centers, European Research Institute, Huawei Technologies Düsseldorf GmbH, Munich, Germany
²Fixed Mobile Engineering Deutschland, Deutsche Telekom Technik GmbH, Darmstadt, Germany
In order to simulate massive deployment of QKD links we introduce a reference network derived from Deutsche Telekom’s real aggregation network. Thereby an area of about 170 km × 140 km is covered and the 39 nodes are connected by 66 fibers. Each of these edges has a particular loss and the simulated QKD links generate corresponding secure key rates. There are different possibilities to populate the network with QKD-links and by combination of different links with the hop-by-hop key distribution method end-to-end keys between all nodes are possible. We discuss and compare different deployment strategies as the MST (Minimum Spanning Tree) and the SSSPT (Single-Source Shortest Path Tree) to achieve high key generation for given use-cases as securing the management, control and data planes.

Alberto Porzio
Continuous variable entanglement over different degree of freedom for entanglement multiplexing
A. Porzio¹, A. Pecoraro¹, F. Cardano², and L. Marrucci^2
1CNR – SPIN Napoli, Italy
²Department of Physics University ”Federico II”, Napoli, Italy
Continuous variable entanglement is usually set between pairs of optical modes sharing the same geometrical property where distinguishability is demanded to polarization and/or frequency. Thus, the inherent non–local correlation shows-up in quantum quadratures relative to two distinct EM modes. In this contribution we will show how the polarization DOF of a pair of entangled modes is coupled to the optical orbital angular momentum giving, at the end, a pair of entangled modes that have orthogonal OAM and polarization. We also show how this experimental scheme can be extended to give more than a pair of entangled modes paving the way to CV entanglement multiplexing.

Mohsen Razavi
Quantum and classical communications on shared infrastructure
S. Bahrani, O. Elmabrok, G. Currás Lorenzo, M. Ghalaii, and M. Razavi
School of Electronic and Electrical Engineering, University of Leeds, UK
Future communications networks not only should enable massive exchange of classical bits, but also the transmission of quantum bits on which many quantum applications rely. This will be the key to offering quantum technologies in a cost-efficient way, and it should encompass the integration of quantum and classical networks at the core of existing optical communications networks, as well as at the access end of such networks. In this work, we cover a range of proposals that enable such an integration for one of the imminent applications of quantum technologies, i.e., quantum key distribution (QKD), by which users can securely exchange a secret key for their cryptographic needs. This will include using wavelength division multiplexing techniques to send quantum and classical data on the same fibre as well as wireless access for QKD users to passive optical networks. In each case, we explore optimal arrangements to find the best way forward for an amicable coexistence.

André Richter
Modelling weak-coherent CV-QKD systems using a classical simulation framework
S. Kreinberg¹, I. Koltchanov¹, P. Novik², S. Alreesh¹, F. Laudenbach³, C.Pacher³, H. Hübel³, and A. Richter^1
1VPIphotonics GmbH, Berlin, Germany
²VPI Development Center, Minsk, Belarus
³Austrian Institute of Technology GmbH, Vienna, Austria
Due to their compatibility to existing telecom technology, continuous variable (CV) weak coherent state protocols are promising candidates for a broad deployment of quantum key distribution (QKD) technology. We demonstrate how our existing simulation framework for modeling classical optical systems can be utilized for simulations of weak-coherent CV-QKD links. The quantum uncertainties for the measured characteristics of coherent signals are modeled in the electrical domain by shot noise, while a coherent signal in the optical domain is described by its quadrature components. We simulate various degradation effects such as attenuation, laser RIN, Raman noise (from classical channels in the same fiber), and device imperfections and compare the outcome with analytical theory. Having complemented the physical simulation layer by the post-processing layer (reconciliation and privacy amplification), we are able to estimate secure key rates from simulations, greatly boosting the development speed of practical CV-QKD schemes and implementations.

Karsten Rottwitt
Quantum information processing using intermodal four-wave mixing in multi-mode optical fibers
K. Rottwitt, J. B. Christensen, E. N. Christensen, and J. G. Koefoed
DTU Fotonik, Technical University of Denmark, Lyngby, Denmark
Essential functionalities in quantum communication are the capabilities of generating and processing quantum states. Examples of the latter include conversion of the wavelength of quantum states or modification of their temporal shape. The combined use of four-wave mixing and higher order modes in optical fibers has enabled such functionalities. The use of intermodal four-wave mixing among higher order modes, enable frequency conversion over a wavelength bandwidth, large enough to avoid spontaneous Raman scattering, which is otherwise detrimental for quantum communication. The process of intermodal four-wave mixing furthermore has the advantage that the same process may be used to generate single photon states, We review recent results on the use of intermodal four-wave mixing in optical multi-mode fibers for quantum information science.

Nuno Silva
Role of device imperfections on the practical performance of continuous-variable quantum key distribution systems
N. A. Silva^1,2, M. Almeida³, D. Pereira¹, M. Facão^3,4, N. J. Muga^1,4, and A. N. Pinto^1,2
1Instituto de Telecomunicações, Aveiro, Portugal
²Department of Electronics, Telecommunications, and Informatics, University of Aveiro, Portugal
³Department of Physics, University of Aveiro, Portugal
⁴I3N, Departamento de Física, Universidade de Aveiro, Portugal
Quantum key distribution (QKD) systems based on the modulation of weak-coherent states and homodyne detection has attracted much attention over last years due to its compatibility with existing telecom equipment. The coherent state required by most of the practical protocols for continuous-variable QKD can be produced in practice using a typical laser source followed by standard phase and amplitude optical modulators. On the other hand, the homodyne detector used to measure the quadratures of the modulated light filed can be implemented with high-efficient PIN photodiodes. Moreover, in continuous-variable QKD systems the security of the secret key depends on the precise estimation by Bob of the loss and excess noise of the quantum channel. In this work we discuss the impact of imperfect state preparation by Alice and the role of homodyne detector imbalance on the performance of a continuous-variable QKD system. More specifically, we will consider that Alice phase and amplitude modulators are not ideal suffering from incorrect modulation calibration and optical imbalance, and that the positive and negative currents of Bob homodyne detector are not completely cancelled due to a non-ideal beam-splitter and due to different quantum efficiencies of its two photodiodes.

Idelfonso Tafur Monroy
Quantum data encryption as a service on demand: Eindhoven QKD network testbed
T. R. Raddo¹, S. Rommel¹, V. Land², C. Okonkwo², and I. Tafur Monroy^1
1Institute for Photonic Integration, Eindhoven University of Technology, The Netherlands
²Eindhoven University of Technology, The Netherlands
The widespread acceptance and deployment of quantum key distribution (QKD) for data encryption requires a better understanding of the technology concerning device-to-system interfacing and network performance from current vendors. Despite the existence of a few QKD testbeds worldwide, they are neither open-access nor capable of validating components from different system and component vendors as well as business cases. User trials in testbeds have yet to yield a robust, open business case. This paper introduces the open-access QKD testbed currently being developed in the Eindhoven region which will focus on the creation of an open environment for end-to-end validation of distinct business cases, QKD security proofs, technology certification and standardization. At this site, quantum-to-the-home network scenario for providing quantum encryption as a service on demand for end-to-end security to end-users is also proposed. It is expected that this testbed will lead to a better understanding of what further developments are required for current networks to be augmented with QKD.

Domenico Tulli
Engineering high-speed quantum random number generators
D. Tulli, C. Abellan, W. and Amaya
Quside Technologies S.L, Castelldefels (Barcelona), Spain
The ability to share information online in a secure way is a major concern for any individual and organization today. In times where we are permanently connected, the development of secure products and infrastructure with long-terms security guarantees is a global priority. Quantum technologies bring in a radically new toolset to realize unbreakable encryption systems as well as to improve randomized algorithms. In this talk, we will discuss recent progress on the integration of high-speed (Gb/s) quantum random number generators. We will share recent operation data from a series of units specifically designed using off-the-shelf telecommunication parts. We will then show application-level results in the fields of encryption and computation and finally, we will show recent progress on the use of photonic integrated circuits for the task of high-speed quantum random number generation, showing the scaling potential of quantum and photonic devices in the cyber-security and super-computation spaces.

Paolo Villoresi
Advances in space quantum communications for new fundamental tests and applications
P. Villoresi, Department of Information Engineering, University of Padova, Italy
In this talk we will discuss how the extension of the spatial scale and the improvement of temporal resolution along Space channels would pave the way for exchanging qubits for both experiments on the interplay of Quantum Physics and Gravitation as well as for new applications of global quantum key distribution.

Alessandro Zavatta
Multiphoton entanglement by delocalized single photon addition
N. Biagi^1,2, L. S. Costanzo^1,2, M. Bellini^1,2, and A. Zavatta^1,2
1Istituto Nazionale di Ottica (INO-CNR), Firenze, Italy
²LENS and Dipartimento di Fisica e Astronomia, Università di Firenze, Italy
We report about the generation of entangled states obtained by applying delocalized single-photon addition between two uncorrelated light modes populated by coherent states. Such entangled states can contain an arbitrary large number of photons while preserving their non-classical correlations. Besides their importance from the fundamental point of view to study quantum effects in large-scale systems, these states are found to be surprisingly robust against losses and thus well suited to travel over long distances and to be stored in atomic ensembles.

RONEXT invited presentations:

Marcelo Abbade
All-optical spectral shuffling of signals traveling through different optical routes
T. de Andrade Bragagnolle¹, M. Pereira Nogueira¹, M. de Oliveira Santos¹, A. J. do Prado¹, A. Alves Ferreira¹, E. A. de Mello Fagotto², I. Aldaya¹, and M. L. F. Abbade^1
1State University of São Paulo (UNESP), SP, Brazil
²Pontifícia Universidade Católica de Campinas (PUC-Campinas), SP, Brazil
Physical layer encryption (PLE) is a promising technology to improve network security. Most PLE techniques are applied to single signals. However, a recent proposal uses an all-optical setup based on spatial light modulators to split two or more wavelength division multiplexing (WDM) signals in several spectral slices and to shuffle these slices. As a result, eavesdroppers aimed to recover information from a single target signal need to handle all the signals involved in the shuffling process. The key space of this all-optical spectral shuffling (AOSS) technique may be as large as the one provided by the safest version of the Advanced Encryption Standard (AES), widely deployed in data cyphering. In this work, we use computer simulations to evaluate the performance of AOSS in a scenario where the shuffled signals travel through different lightpaths. From the security point of view, this is an interesting possibility, because it obliges eavesdroppers to tap different optical fibres/ cables. On the other hand, each shuffled signal experiences different physical impairments and the deleterious consequences of these effects must be accurately compensated in the receiver that deshuffles the signals. In particular, we focus on the influence of dispersion compensation on the bit error rate performance of the recovered signals.

Carmelo Bastos-Filho
OTN network planning over DWDM using computational intelligence
J. C. da Silva, C. J. A. Bastos-Filho, R. C. Almeida-Júnior, D. A. R. Chaves, D. R. B. Araújo, A. V. S. Xavier, and J. F. Martins-Filho
Polytechnic School of Pernambuco, University of Pernambuco, Recife-PE, Brazil
With the increasing demand for high-quality telecommunications services, new technologies have been introduced in the optical networking market. Among them, we can cite optical transport networks (OTNs) that work as a layer above the DWDM network and allow more efficient use of resources. The present work proposes a methodology for planning OTN networks over DWDM based on meta-heuristics. The primary objective is to enable the minimization of the cost with OTN interfaces (element with the most significant cost) in the network simultaneously satisfying the requirements of performance and resilience. We deployed the NSGAII algorithm to minimize two conflicting objectives in a network with static traffic: number of network interfaces and number of failures in the restoration processes considering all the possible combination of double failures. In this first version of the optimizing process, we used classical operators for selection, crossover, and mutation. We used a scenario to validate the methodology composed by a network with 4 OTN nodes. We performed 30 trials to allow statistical analysis. For the sake of comparison, we compared the results of the proposal with the optimum solution obtained by the simulation of all the cases. We observed a reduction in the number of interfaces for our proposal. The results suggest that the model employed can perform the planning of the OTN layer.

Andrea Fumagalli
Performance evaluation of two service recovery strategies in cloud-native radio access networks
S. Ramanathan¹, K. Kondepu², B. Mirkhanzadeh¹, M. Razo¹, M. Tacca¹, L. Valcarenghi², and A. Fumagalli^1
1Open Network Advanced Research lab, The University of Texas at Dallas, USA
²Scuola Superiore Sant’Anna, Pisa, Italy
Through the virtualization of network functions (VNFs) Cloud-native radio access network (C-RAN) architectures bring several advantages to mobile virtual network operators, such as reduced cost, improved flexibility, scalability, and security. However, when these VNFs are affected by Cloud failure or maintenance, the service downtime perceived by the C-RAN mobile user should be minimized if possible. This study investigates experimentally the C-RAN mobile user service downtime in the presence of a failing virtual evolved packet core (vEPC) when two alternative recovery mechanisms are applied: i) a live migration of the vEPC from the affected data center to a backup data center, and ii) the use of multiple geo-diverse mobility management entities (MMEs), which is a functionality available in S1-flex supported by OpenAirInterface. The study accounts for a Software Defined Networking (SDN) optical backhaul network that consists of OpenROADM equipment configurable through the TransportPCE Controller and PROnet resource Orchestrator. Results suggest that the former mechanism be used as a proactive recovery and therefore activated when the vEPC failure is predictable, whereas the second mechanism be used as a reactive recovery and therefore activated to overcome unexpected and sudden vEPC failure occurrences.

Marija Furdek
Enhancing optical network security with machine learning
M. Furdek and C. Natalino
KTH Royal Institute of Technology, Sweden
As the critical communication infrastructure, optical networks have a vital role in safe and dependable transmission of massive amounts of data, supporting essential societal services. However, these networks are inherently vulnerable to a multitude of deliberate, man-made attacks targeting service disruption at the physical layer. Managing physical-layer security requires timely and accurate detection of physical-layer attacks as a prerequisite for fast and effective attack response and network recovery. In this paper, we present how different data analytics and machine learning approaches can be applied to interpret the optical performance monitoring data in order to identify anomalous operation and trigger security threat warnings.

Silvia Pato
Reliable and cost-effective optical transport networks exploiting shared regenerator pools for optical restoration
J. Pedro and S. Pato
Infinera, Amadora, Portugal
The availability of flexible line interfaces and advanced reconfigurable optical add/drop multiplexers (ROADMs) and the adoption of software-defined networking (SDN) controllers opens new opportunities to design and operate optical networks more cost-effectively. Particularly, it becomes possible to improve network resilience via optical restoration without incurring large capital expenditures. This is attained by deploying pools of shared regenerators at specific network nodes and optimally using them to proactively set up restoration paths in response to a first failure event. In this context, this paper overviews the underlying network architecture and key building blocks and introduces different strategies to size the pools of shared regenerators. The performance of these strategies is compared via simulation over a reference network topology.

Carla Raffaelli
Dedicated path protection for reliable network slice embedding based on functional splitting
B. M. Khorsandi, F. Tonini, E. Amato, and C. Raffaelli
University of Bologna, Italy
In the 5G context new services can be designed using slice configuration in relation to target performance. Service slice embedding on the network infrastructure can be provided by considering the functional splitting known as xhaul. With reference to this approach, novel slicing deployment strategies for 5G are presented to provide resiliency while optimizing the use of optical and computational resources.

Gangxiang Shen
Distributed backup resource allocation in fiber-wireless (FiWi) access networks supporting mobile edge computing
Tong Wang¹, Shuiping Jie², Boping Jiang², S. K. Bose³, and Gangxiang Shen^1
1School of Electronic and Information Engineering, Soochow University, Suzhou, China
²Zhongtian Broadband Technology, Rudong, China
³Department of Electronics and Electrical Engineering, Indian Institute of Technology Guwahati, India
We propose a distributed backup resource allocation scheme to enhance the reliability of mobile edge computing (MEC) services in a Fiber-Wireless (FiWi) access network. An Integer Linear Programming (ILP) model is developed to formulate the backup resource allocation problem to minimize the size of the MEC server at each node and the total backup capacity in a FiWi access network. An efficient heuristic algorithm is also developed to decide the backup MEC resources at each MEC server based on the bucket effect (BE). Simulation results demonstrate the effectiveness of the proposed approaches.

Marco Tacca
Demonstration of an OpenROADM SDN-enabled network for geo-distributed data centers
B. Mirkhanzadeh¹, A. Shakeri¹, D. Bhardwaj², S. Vachhani², M. Birk², M Lyonnais³, J. Kunz³, T. Locke³, G. Sutherland⁴, Yong Chao Fan⁴, Jian Zhang⁴, M. Dalglish⁴, L. Hogan⁴, C. Betoule⁵, G. Thouenon⁵, A. Triki⁵, G. Lambert⁵, O. Renais⁵, G. Vania¹, M. Razo¹, M. Tacca¹, T.Culver¹, and A. Fumagalli^1
1Open Networking Advanced Research (OpNeAR) Lab, UT Dallas, TX, USA
²AT&T Labs, Middletown, NJ, USA
³Ciena, Hanover, MD, USA
⁴Fujitsu Network Communications, Richardson, TX, USA
⁵Orange Labs, Lannion, France
Data centers host critical components for the correct and efficient functioning of many business sectors. Any interruptions in data center operations can bring down an entire business, unless an efficient backup strategy is devised. The use case envisioned in this demonstration consists of a backup data center that can temporarily substitute for the primary data center in the presence of an imminent disaster. The backup and primary data centers, which must be located at a sufficient geographical distance from one another to guarantee geo diversity, are interconnected by a programmable optical fiber network (called PROnet) consisting of OpenROADM certified equipment from vendors and an open source OpenDaylight Controller based on the TransportPCE project. Upon detection of an imminent disaster affecting the primary data center, the SDN PROnet Orchestrator executes an automatic procedure which live migrates the Virtual Machines (VMs) currently running at the primary data center, to the backup data center in the shortest possible time interval. To achieve this goal, the PROnet Orchestrator makes concurrent use of three open source platforms: OpenROADM, OpenFlow, and OpenStack. The Open ROADM platform is used to dynamically establish a high data rate optical circuit between the two data centers, the OpenFlow platform is used to establish a data flow between the top of the rack switches of two compute node racks, one at the primary and one at the backup data center, and the OpenStack platform is used to execute the live migration of the VMs over the newly created optical circuit. The procedure terminates once all of the VMs are successfully running at the backup data center and both the data flow and optical circuit are relinquished.

Luis Velasco
Adaptation of the residual signal for filter failure detection in scenarios with multiple filter types
S. Barzegar, M. Ruiz, and L. Velasco
Optical Communications Group (GCO), Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
Failure detection is of paramount importance in optical networks as a result of the huge amount of traffic that optical connections support, so recovery techniques can be applied. In this paper, we rely on Optical Spectrum Analyzers (OSA) deployed in the optical nodes as monitoring devices acquiring the optical spectra of outgoing links. Analyzing the optical spectrum of optical connections, specific soft-failures that affect the shape of the spectrum can be detected, like Filter Shift and Filter Tightening. We present a residual-based approach spectra analysis that uses a set of residual signals calculated by subtracting the measured signal by the OSA from an expected version of the signal. Exhaustive experiments are carried out to show the performance of the proposed approaches under filter failures.

Moshe Zukerman
Path planning of submarine cables
Qing Wang, Zengfu Wang, Jun Guo, Elias Tahchi, Xinyu Wang, Bill Moran, and M. Zukerman
City University of Hong Kong, China
Submarine optical-fiber cables are key components in the conveying of Internet data, and their failures have costly consequences. Currently, there are over a million km of such cables empowering the Internet. To carry the ever-growing Internet traffic, additional 100,000s of km of cables will be needed in the next few years. At an average cost of $28,000 per km, this entails investments of billions of dollars. In current industry practice, cable paths are planned manually by experts. This paper surveys our recent work on cable path planning algorithms, where we use several methods to plan cable paths taking account of a range of cable risk factors in addition to cable costs. Two methods, namely, the fast marching method (FMM) based and the Dijkstra’s algorithm are applied here to long-haul cable path design in a new geographical region. A specific example is given to demonstrate the benefit of the FMM-based method in terms of the better path planning solutions over the Dijkstra’s algorithm.

SDM-WDM invited presentations:

Josep Fabrega
Digital radio-over-fiber transceivers for SDM/WDM front- and back-haul
J. M. Fabrega¹, R. Muñoz¹, M. Svaluto Moreolo¹, L. Nadal¹, M. Eiselt², F. Azendorf², J. P. Turkiewicz³, P. W. L. van Dijk⁴, S. Rommel⁵, and I. Tafur Monroy^5
1Centre Tecnològic de Telecomunicacions de Catalunya (CTTC/CERCA), Castelldefels, Barcelona, Spain
²ADVA Optical Networking SE, Munich, Germany
³Orange Polska, Warsaw, Poland
⁴LioniX International, Enschede, The Netherlands
⁵Eindhoven University of Technology, The Netherlands
In this paper we analyze the perspective of digitized radio over fiber (DRoF) fronthaul, showing how to meet the requirements to cope with the future radio access networks (RANs). This entails the introduction of space division multiplexing (SDM) while increasing the flexibility and capacity of the DRoF transceivers. Since the evolution of the DRoF fronthaul is being revised and re-defined, in the blueSPACE project we propose two different DRoF transceiver options: DRoF-A and DRoF-B. In DRoF-A, a simple transceiver is proposed, based on the recent standard specifications and, therefore, expected to be deployed in the short-term. Along a different line, DRoF-B is a more advanced transceiver that features high flexibility, relying on a strong DSP and targeting a long-term deployment. Besides a basic characterization of both solutions, we also analyze additional aspects related to the design and implementation of these two DRoF solutions and their integration into an SDM based RAN. This includes the programmability and interaction with the control plane.

Darli Mello
Scanning-based chromatic dispersion estimation in mode-multiplexed optical systems
R. S. B. Ospina¹, L. F. dos Santos¹, D. A. A. Mello¹, and F. M. Ferreira^2
1School of Electrical and Computer Engineering, State University of Campinas UNICAMP, Brazil
²Aston Institute of Photonic Technologies, Aston University, Birmingham, UK
Mode-multiplexed coherent optical systems emerge as an alternative to overcome the capacity limits of current optical communication systems. As in single-mode systems, mode-multiplexed transmission experiences accumulated chromatic dispersion that must be estimated and compensated for by digital signal processing. Although scanning-based methods are widely used to estimate chromatic dispersion in single-mode optical systems, their performance in mode-multiplexed systems has not been evaluated. In this paper, we study three scanning-based chromatic dispersion estimation techniques in the scope of mode-multiplexed optical systems. The results indicate that the three algorithms loose accuracy for high levels of crosstalk and ASE noise. However, we show that the delay-tap sampling method can be properly modified to significantly improve the estimation performance, even in the worst-case evaluated crosstalk scenario.

Naoya Wada
Multi-granular optical networks based on SDM technologies
Y. Hirota, R. S. Luis, H. Furukawa, and N. Wada
National Institute of Information and Communications Technology (NICT), Tokyo, Japan
We present a recently developed multi-granular optical network testbed with spatial super channel switching technologies.

SWP invited presentations:

Pierre-Michel Adam
Surface enhanced spectroscopies of ZnO nanostructures
P-M. Adam, Light, nanomaterials and nanotechnologies (L2n), Université de Technologie de Troyes, France
Plasmonics deals with surface plasmons at the subwavelength scale. It has highly potential applications for nanoscale and ultrafast photonics. Understanding the coupling properties between quantum emitters and plasmons resonances and/or nanoantennas is a key step towards realistic applications in the near future. We will present in this paper our latest experimental and theoretical results on surface enhanced spectroscopies, consisting in emitters coupled to different types of surface plasmons excitations, localized plasmons on bimetallic nanoparticles and surface plasmons polaritons on waveguides.

Yossef Ben-Ezra
The influence of the excited state lasing in quantum dot-in-a-well (QDWELL) structure on the QDWELL laser performance in optical communication systems
Y. Ben Ezra^1,2 and B.I. Lembrikov^1
1Faculty of Electrical Engineering and Electronics, Holon Institute of Technology, Israel
²MER Cello, Holon, Israel
Quantum dot (QD) lasers and semiconductor optical amplifiers (SOA) are promising candidates for the new generation of optical communication systems due to their unique properties such as ultrafast dynamics, low threshold, temperature stability, large spectral bandwidth, low energy consumption, compatibility with modern micro- and nanotechnologies [1], [2]. These features are due to the three-dimensional (3D) confinement of carriers in QDs [1], [2]. The QD laser and SOA performance may be improved by using the QD-in-a-well (QDWELL) structure where QDs are embedded into the quantum well (QW) layers [3]. In such a case, carriers in a reservoir are also confined into QW representing a two-dimensional (2D) gas [3]. The carrier dynamics in QDWELL structures is determined by strongly nonlinear scattering processes between QW and QD [3]. In a QD there exist two states: a ground state (GS) and an excited state (ES) [3]. Typically, the fast ES-GS transitions are neglected, and only the GS lasing is taken into account [3]. The carrier dynamics influence on the QD laser and SOA performance in optical communication systems for the case of the GS lasing have been analyzed theoretically [4]-[6] (see also references therein). We solved numerically the system of rate equations describing the transitions between the carrier reservoir wetting layer (WL) and GS. However, QD lasers can exhibit simultaneous GS and ES lasing [7]. The theoretical model including the GS and ES had been developed and the dynamics of two-state lasing had been investigated [7]. In this paper, we used the two-state lasing approach [7] in order to investigate the ES lasing influence on the QDWELL laser performance in optical communication systems.
[1] E. U. Rafailov, M. A. Cataluna, E. A. Avrutin. Ultrafast Lasers based on Quantum Dot Structures. Wiley, 2011.
[2] V. M. Ustinov, A. E. Zhukov, A. Yu. Egorov, N. A. Maleev. Quantum Dot Lasers. Oxford University Press, 2003.
[3] K. Lüdge. Modeling quantum-dot-based devices. Nonlinear Laser Dynamics. Edited by K. Lüdge. Wiley, 2012, pp. 3-33.
[4] Y. Ben Ezra, B. I. Lembrikov. Ultra-fast all-optical memory based on quantum dot optical amplifiers (QD-SOA). Optical Fiber and Wireless Communications. Edited by R. Roka. INTECH, Croatia, Rijeka, 2017, pp. 279-293.
[5] Y. Ben Ezra, B. I. Lembrikov. Improvement of the quantum dot-in-a-well laser and amplifier performance under the optical injection. Optical Communication Technology. Edited by P. Pinho. INTECH, Croatia, Rijeka, 2017, pp. 74-99.
[6] Y. Ben Ezra, B. I. Lembrikov. Quantum dot-semiconductor optical amplifiers (QD-SOA): Dynamics and applications. Optical Amplifiers-A Few Different Dimensions. Edited by P.K. Choudhury, IntechOpen, London, UK, 2018, pp. 10-38.
[7] A. Röhm, B. Lingnau, K. Lüdge. Understanding ground-state quenching in quantum-dot lasers. IEEE Journal of Quantum Electronics, vol. 51, no. 1, 2000211-1-11, Jan. 2015.

Louise Bradley
Tuning metasurfaces with phase change materials
S. Cunnningham, S. Barry Porter, P. Stamenov, C. Hrelescu, and A. L. Bradley
Department of Physics and CRANN, Trinity College Dublin, Ireland
Over the past decade, plasmonic structures and metamaterials have been intensively investigated for the control of electromagnetic radiation. The optical response is determined by the combination of materials, geometry and structure dimensions. For many optoelectronic applications the inability to tune the optical response post-fabrication limits functionality. To overcome this, we consider tuneable elements formed by coupling plasmonic components with a phase change material. Results showing the dynamic properties of metasurfaces will be presented.

Pierre-Francois Brevet
A tentative comprehensive overview of the second harmonic generation from plasmonic nanoparticles
Z. Behel and P.-F. Brevet
Institut Lumière Matière, Université Claude Bernard Lyon 1, Villeurbanne, France
Fundamental studies on the nonlinear optical properties on a series of plasmonic nanoparticles have been performed over the last years [1]. In this respect, Second Harmonic Scattering (SHS) of aqueous suspensions of these nanoparticles is an ideal method of characterization because of the absence of any substrate. This is indeed a requisite for even order nonlinear optical phenomena where symmetry is critical in providing an unbiased response that could otherwise arise from the substrate itself. From the current data available for the SHS response from metallic nanoparticles of different size or shape, a general view can be built [2]. Understanding the origin of the response has been at the center of the attention in order to design nanoparticles with the best cross-sections, also known as first hyperpolarizabilities, for the SHS process and therefore applications like sensing for example. However, beside size and shape, the material and the morphology is also an interesting route that has been recently explored to further develop new systems. The presentation will address these key aspects in light of our recent results where we have investigated both centrosymmetric and non-centrosymmetric metallic nanoparticles as well as different morphologies like plain metallic or dielectric core – metallic shell nanoparticles [3]. All these studies allow us to provide a comprehensive picture of the SHS response from plasmonic nanoparticles. This overview will be recast in the general context of nonlinear optics at the nanoscale and the opening of new avenues for applications.
[1] J. Butet, P.F. Brevet, O.J.F. Martin, Optical second harmonic generation in plasmonic nanostructures: From fundamental principles to advanced applications, ACS Nano, 9 (2015) 10545-10562
[2] J. Butet, et al., Second harmonic generation with metallic nanoparticles, Metal Nanostructures for Photonics, Elsevier, Amsterdam, 2018.
[3] I. Russier-Antoine, et al., Second harmonic scattering from silver nanocubes, J. Phys. Chem. C, 122 (2018) 17447-17455.

Svatopluk Civiš
Photochemical reduction of CO₂ on terrestrial planets
S. Civiš¹, A. Knížek^1,2, M. Ferus¹, and P. Kubelík^1
1J. Heyrovský Institute of Physical Chemistry, v.v.i, Academy of Sciences of the Czech Republic, Prague, Czech Republic
²Charles University, Faculty of Sciences, Department of Physical and Macromolecular Chemistry, Prague, Czech Republic
³Institute of Physics, Czech Academy of Sciences, Praha, Czech Republic
The origin of methane on Mars and other terrestrial planets in their early or late stages of chemical evolution has never been explained in a satisfactory way. Here we propose a photochemistry-based scenario of carbon dioxide reduction to methane on semiconductor photocatalysts, such as TiO₂. This approach takes inspiration in the same reaction chain used in environmental chemistry research since the late 1970s. On Mars, this scenario could unveil the origin of methane, which has been hotly debated recently. On young extra-terrestrial planets, this process could supply the atmosphere with reduced gases and facilitate organic synthesis and possibly the origin of life in these new born worlds.

Crina Cojocaru
Phase locked harmonic generation in the opaque region of GaAs
C. Cojocaru¹, L. R. Suñé¹, M. Scalora², and J. Trull^1
1Physics Department, Universitat Politècnica de Catalunya, Terrassa, Barcelona, Spain
²Charles M. Bowden Research Center, AMRDEC, RDECOM, Redstone Arsenal, AL, USA
We demonstrate second and third harmonic generation from a GaAs substrate, well-below the absorption edge, in both transmission and reflection geometries. The pump is tuned at 1064 nm, in the transparency range, while the SH and the TH signals are tuned in the opaque spectral range of GaAs, at 532 nm and 355 nm, respectively. As expected, we find that the polarization of the generated signals is sensitive to the polarization of the pump. In our experiment, we work far from the phase matching condition and we account for both surface and bulk contributions, and show that the surface-generated SH components can be more intense than bulk-generated SH signals. The experimental results are contrasted with numerical simulations that include these two factors, using a hydrodynamic model that accounts for all salient aspects of the dynamics, including surface and bulk generated harmonic components.

Stelios Couris
Graphene(s): Tuning their nonlinear optical response
S. Couris^1,2, I. Papadakis^1,2, Z. Bouza^1,2, A. Stathis^1,2, N. Karampitsos^1,2, D. Kyrginas^1,2, M. Stavrou^1,2, and D. D. Ziaka^1,2
1Department of Physics, University of Patras, Greece
²Institute of Chemical Engineering Sciences (ICE-HT), Foundation for Research and Technology, Hellas (FORTH), Patras, Greece
Pristine graphene, graphene oxide and fluorographene are among the most studied members of the family of two-dimensional (2D) materials. The interest for these materials has been boosted by their extraordinary properties which have been objects of numerous and extensive investigations during the last years. Their fascinating properties are basically due to their structure, being a single layer of carbon atoms, arranged in a 2D honeycomb lattice. This structural arrangement has dramatic consequences on the formation of their electronic bands giving rise to a unique conical band structure converging to a single Dirac point, making their electrons having some unique properties (as e.g. absorption of ~2.3% per layer, electrons moving with relativistic speed, Pauli blocking effect, resonant character of excitation everywhere from the UV to IR, etc.). Pristine graphene exhibiting sp3 hybridization, has a zero-bandgap behaving like a metal, while its oxidation and/or fluorination leads to partial transformation of the sp3 hybridization to a mixture of sp3-sp2 hybridizations which give rise to a sizeable bandgap which can be modulated with the degree of functionalization. In the present work, we will review our very recent results concerning the nonlinear optical properties of graphene, graphene oxide and graphene fluoride determined using nanosecond, picosecond and femtosecond laser excitation. Additionally, the effect of the number of layers and the degree of oxidation and/or fluorination on the NLO response will be presented and discussed as well.

Cid de Araújo
Nonlinear photonics with metal-dielectric nanocomposites
C. B. de Araújo, Universidade Federal de Pernambuco, Recife, PE, Brazil
In this communication some of our works on nonlinear (NL) photonics with metal-dielectric nanocomposites (MDNCs) will be reviewed. The optical response of the MDNCs was controlled by selecting the metal nanoparticles (NPs) composition, shape, density, and spatial arrangement, as well as by the appropriate choice of the NPs hosts. High-order nonlinearities, beyond the usually studied third-order nonlinearity, were characterized. The NL propagation of light was studied and the stability and guiding of spatial solitons were investigated. A procedure for optimization of all-optical switches, the upgraded operation of an optical amplifier in the short-wave infrared region (SWIR), the optical modulation based on the dynamic control of gold nanorods driven by an external electric field, and the study of a NL metasurface in the SWIR, will be described to exemplify possible applications of MDNCs.

Richard De La Rue
Biomedical optical sensing using nano-/micro-structured metamaterials
I. F. M. A. Nasri, I. Mbomson, G. J. Sharp, R. M. De La Rue, N. P. Johnson, M. Sorel, and C. Gauchotte-Lindsay
School of Engineering, University of Glasgow, UK
Work on optical sensing techniques for biomedical and other related applications continues to advance. Integrated devices that are fabricated by means of classical planar technologies have a central role in the development of low-cost and reliable sensors, at both the molecular and cell levels. Resonant structures based on both photonic crystal microcavities and on metamaterial/plasmonics concepts are of continuing interest, while cavities in the form of waveguide ring resonators are competitive.  Waveguide Mach-Zehnder structures can also provide the sensitivity required for successful application. Fluorescent labelling has been demonstrated as a viable approach in biomedical sensing, e.g. for carrying out competition immunoassays to identify the possible presence of specific analyte molecules in suitably prepared fluid samples. But the alternative approach of label-free biomedical sensing seems likely to be favoured in future applications.  Designed tuning of reflection, transmission and absorption resonances can be used to help identify specific molecules, through selection of the known bond resonances of the molecules of interest. Since it is typically possible to organise resonant structures in arrays that consist of thousands of individual resonant ‘atoms’, thereby forming a metasurface, it has become possible to select and quantify various characteristic molecular bond resonances simultaneously – and to identify possible molecular compositions. Structured surfaces such as photonic crystal waveguide slabs can provide valuable increases in signal strength for optical microscopy, e.g. in photonic crystal-enhanced microscopy (PCEM).  This presentation will provide an overview of some recent progress in the domain of optics-based bio-medical sensing.

Piotr Dulian
Preparation of functional thin oxide coatings on the surface of cenospheres by fluidized bed chemical vapour deposition method
P. Dulian¹, D. Bradło¹, W. Żukowski¹, and J. Jaglarz^2
1Faculty of Chemical Engineering and Technology, Cracow University of Technology, Poland
²Faculty of Materials Engineering, Cracow University of Technology, Poland
An effective method for producing thin oxide coatings on the surface of cenospheres using the fluidization technique will be illustrate in the presentation. Because of the unique properties, especially their low density, cenospheres are very promising support for various types of catalysts, including photocatalysts. An efficient way of oxide layers production on their surface is currently difficult due to their spherical shape and micrometric sizes. The fluidized-bed chemical vapour deposition (FB-CVD) method makes it possible to apply the active phase on the surface of the cenospheres in a relatively simple and effective manner. The results of detailed both structural and electro-optical studies as well as the photocatalytic properties of the resulting catalyst will be shown and discussed.

Abdel El Abed
One-step synthesis of highly monodisperse ZnO core-shell microspheres in microfluidic devices
N. Ghifari^1,2, A. Chahboun², and A. El Abed^1
1Laboratoire de Photonique Quantique et Moléculaire,  ENS Paris Saclay and Centrale Supélec, Cachan, France
²Laboratoire des Couches Minces et Nanomatériaux, Faculté des Sciences et Techniques de Tanger,  Université Abdelmalek Essaadi, Morocco
The controllable fabrication of highly monodisperse dielectric and semiconductor microspheres with tunable particle size and morphology has gained more and more interest for many scientific and technological applications. In this work, we report a facile method for the fabrication of monosized zinc oxide (ZnO) microcapsules with a combination of sol-gel and droplet microfluidics techniques. The as-synthesized microspheres were analysed and characterized using optical and scanning electron microscopies. The effect of droplet stabilizing surfactant and the flow rates of the continuous and the dispersed phase on droplet size were investigated. The results show that the synthesized ZnO microspheres exhibit excellent monodispersity with a hollow feature whose thickness was found about 0.7 µm, in agreement with theoretical calculations.

Abdelkrim El-Ghayoury
Azo-based ligands and metal complexes for NLO applications
A. El-Ghayoury, A. Ayadi, B. Kulyk, and B. Sahraoui
MOLTECH-Anjou Laboratory, UMR CNRS 6200, University of Angers, France
New generations of the optoelectronic devices for communications, optical switching and information storage require the development of materials with exceptional nonlinear optical (NLO) response [1]. Thus, organic materials, polymeric materials, organometallic or coordination metallic complexes as well as new hybrid organic/inorganic nanocomposites have been the subject of both experimental and theoretical investigations during many years because of their valuable potential applications in photonics and optical devices. Azobenzenes that are functionalized with an electron-donor and/or electron-acceptor groups exhibit attractive optical and nonlinear optical properties. The photoinduced trans-cis isomerization that occurs in these materials is the basis for many functional materials with applications in nonlinear optics, optical storage media, chemosensors and optical switches. In contrast combining such photochromic units with a coordinating or a binding unit is a very successful strategy for the design of photochromic transition metal complexes [2]. We have been recently interested in the synthesis and characterization of both electroactive and photoactive ligands and in their use as active materials for nonlinear optical applications. These NLO properties could be modulated by the metal coordination of these different ligands [3-5]. In this presentation a focus will be made on first the chemical synthesis and characterization of the ligands and their corresponding metal complexes using d-transition metal cations such as Zn(II) (see the figure below) , Ag(I), Re(I),… Then we will discuss about the valuable potential to be used in photonics by studying their nonlinear optical properties. A particular interest will be on the effect of the nature of substituents within this ligands and then on the effect of the nature of the metal used.
[1] P. N. Prasad, D. J. Williams, Introduction to Nonlinear Optical Effects in Molecules and Polymers, Wiley: New York, 1991.
[2] A. Bianchi, E. Delgado-Pinar, E. García-España, C. Giorgia, F. Pina, Coord. Chem. Rev. 260, 156-215 (2014).
[3] I. Guezguez, A. Ayadi, K. Ordon, K. Iliopoulos, D. G. Branzea, A. Migalska-Zalas, M. Makowska-Janusik, A. El-Ghayoury, B. Sahraoui, J. Phys. Chem. C 118, 7545-7553 (2014).
[4] A. Ayadi, D. G. Branzea, M-A. Benmensour, A. Boucekkine, N. Zouari, A. El-Ghayoury,. Tetrahedron, 71, 7911-7919 (2015).
[5] B. Kulyk, D. Guichaoua, A. Ayadi, A. El-Ghayoury, B. Sahraoui, Organic Electronics 36, 1-6 (2016).

Didier Felbacq
Field representation for the scattering of electromagnetic waves by several obstacles
A. Gourdin, P. Genevet, and D. Felbacq
Laboratoire Charles Coulomb, Universitè de Montpellier, Montpellier, France
The design of complex structures such as metasurfaces requires the development of efficient numerical methods, so as to deal with possibly aperiodic structures. During an optimisation process, it is necessary to perform many computation at the same wavelength while the position and properties of the scatterers are varied. We propose here a numerical scheme that allow to pre-calculate the scattering properties of arbitrary bodies in order to enhance the efficiency of the optimisation process. The method is based on a representation of the field by means of fictitious sources decomposed on a modal basis adapted to the geometry of the scatterer.

Joaquín Fernández
Spectroscopic properties and modeling of Nd³⁺ random lasers
I. Iparraguirre¹, J. Azkargorta¹, R. Balda^1,2, and J. Fernández^3
1Departamento de Física Aplicada I, Escuela Superior de Ingeniería, Universidad del País Vasco UPV/EHU, Bilbao, Spain
²Materials Physics Center CSIC-UPV/EHU, San Sebastián, Spain
³Donostia International Physics Center, San Sebastián, Spain
This work presents a comparative study among the spectroscopic properties of near infrared random lasers based on stoichiometric Nd crystal powders. A model based on a probability distribution of the stimulated photon paths lengths in the sample, as well as on the population inversion shared by different photon paths, satisfactorily compare with the results of laser threshold and absolute input/output energy slope of a real Random Laser. A comparative study of the random lasing performance of several Nd based stoichiometric compounds, together with a discussion about the fundamental parameters which control the random laser operation are presented. Moreover, we demonstrate that a Nd-based crystal powder random laser provides Speckle-free transmission and reflection infrared images with higher values of contrast to noise ratio (CNR) than those obtained with the narrowband laser. These results open up new possibilities to enhance the field of high resolution imaging for optoelectronic and biomedical applications.

Jean-Luc Fillaut
Polypyridyl ruthenium complexes: Versatile tools for linear and non-linear optics
N. Durand¹, H. Akdas-Kilig¹, A. Boucekkine¹, A. Spanenberg², J-P. Malval², J-L. Fillaut^1
1Institut des Sciences Chimiques de Rennes, UMR 6226 CNRS – Université de Rennes, France
²Institut de Science des Matériaux de Mulhouse, UMR 7361CNRS – Université de haute-Alsace, Mulhouse, France
Molecules with π-conjugated electronic structures have been attracting considerable interest in relation with their potential nonlinear optical (NLO) properties and applications in optoelectronic and photonic devices. The first investigations were initially focused on purely organic systems. The search for alternative organometallic and inorganic derivatives has gradually intensified in the last years. Indeed, it readily appear s that incorporation of metal atoms into π-conjugated systems may introduce many new variables, such as diversity of oxidation states, intensely colored charge-transfers, additional magnetic capabilities, and a diversity of topologies, which leads to NLO chromophores of much greater complexity than that of the first generation of “push-pull” organic molecules. In particular, ruthenium complexes have provided intriguing molecular materials with unusual electronic capabilities. The chemical, photochemical, and electrochemical behavior of hundreds (pyridine)ruthenium(II) complexes, the parent complex being [Ru(bpy)₃]²⁺ has been extensively investigated in the past 30 years. In these (pyridine)ruthenium(II) complexes, the metal center is engaged in π-bonding with the organic ligating groups, and hence provides various candidates for NLO applications. Other reasons for this interest are the possibility of designing various promising octupolar topologies. We will discuss the design of multifunctional polypyridyl ruthenium(II) complexes, that associate ligands with high intramolecular charge transfer transitions, to afford two-photon absorption properties, together with various functional units. The linear and non-linear optical characterization of these complexes will be discussed as well as their processing as optically active molecular materials for specific applications.

Céline Fiorini-Debuisschert
Plasmonic nano-objects: From subwavelength field enhancement to hot charges and luminescence
C. Molinaro¹, S. Marguet², L. Douillard¹, F. Charra¹, and C. Fiorini-Debuisschert^1
1SPEC, CEA, CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
²NIMBE, CEA, CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
Plasmonic luminescence has been the subject of intense work and debates over the last years, a lot of studies more particularly regarding gold particles. Although bulk gold is known to present very low luminescence quantum yield, gold nanoparticles can indeed present a huge nonlinear luminescence with an apparent high influence of the particle shape. In the case of nanorods (NRs), we could show that their large two-photon luminescence (TPL) is the result of a so-called “double antenna effect” in direct connection with their two different localized surface plasmon resonances. Excitation of gold NR at its longitudinal plasmon frequency (above 750 nm) first lead to increased absorption and thus increased production of electron-hole pairs that happen to recombine radiatively through the transverse plasmon band i.e. with an enhanced emission at the NR transverse plasmon band (around 520/540 nm). Such behaviour could also be evidenced in the case of colloidal gold nanobipyramids exhibiting non only dipolar but also higher order plasmon resonances. Our aim is now to determine the exact parameters enabling to control and optimize the radiative electron-hole recombination for a given localized plasmon resonance. Above luminescence we will also discuss other processes originating from plasmon relaxation, from photothermal effects to hot charges induced photochemistry.

Stavroula Foteinopoulou
Slow-light waveguides in the practical realm
S. Foteinopoulou, Electrical and Computer Engineering Department, University of New Mexico, Albuquerque, USA
Waveguide systems for slow-light propagation have attracted increased attention in the last decade owing to their promising capabilities for delaying, trapping and enhancing EM fields. These capabilities are of high interest in modern photonics systems and applications such as integrated photonics or frequency conversion and mixing platforms. Despite the intense research efforts in this research area it appears that significant obstacles remain in utilizing the full potential of slow-light waveguide systems for practical applications. We discuss here what are the challenges in meeting application demands with slow-light waveguide systems. Based on these we propose design principles that would lead to better performing slow-light waveguides. By utilizing specific examples of metamaterial-based waveguides we apply these design principles and verify that they lead to high-performing systems with large light slow-down factors and EM intensity enhancement.

Konstantin Gaikovich
Achievements and prospects in near-field subsurface diagnostics
L. A. Bokeria¹, T. T. Kakuchaya¹, V. A. Badeev², Y. S. Maksimovicth², A. I. Smirnov³, and K. P. Gaikovich^4
1A.N. Bakulev National Medical Research Center of Cardiovascular Surgery, Moscow, Russia
²Institute of Applied Physics, NAN of Belarus, Minsk, Belarus
³Institute of Applied Physics RAS, Nizhny Novgorod, Russia
⁴Institute for Physics of Microstructures RAS, Nizhny Novgorod, Russia
Various methods of near-field diagnostics of subsurface inhomogeneities based on the solution of inverse scattering problems have been developed and demonstrated in experiments by now. This approach provides a subwavelength resolution in tomography and holography of 3D distributed inhomogeneities as well as in the profiling (retrieval of depth profiles) of one-dimensional inhomogeneities. Here we present main achievements in these studies and propose new methods developed for diagnostics of frequency dispersive inhomogeneities in multilayer media and for targets with nonlinear susceptibility. Obtained results of numerical simulations and experimental studies demonstrate possibilities of their applications in biomedical diagnostics and non-destructive testing.

Ramon Galatus
Low-cost distributed angle sensor implemented on a fluorescent fiber
R. Galatus, P. Farago, S. Hintea, and D. Mogą
Technical University of Cluj-Napoca, Romania
This work proposes the fluorescent fiber implementation of an angle sensor. The distributed nature of the proposed sensor allows the simultaneous assessment of multiple angles, whereas the fluorescent fiber allows for a low-cost implementation of the module. The distributed sensing technique is based on the frequency encoding of the bending positions along the fluorescent fiber, whereas angle sensing is performed by assessing the intensity of the fluorescent radiation generated at each bending position respectively. Accordingly, the signal transmitted along the fiber consists of a superposition of DC components corresponding to the generated fluorescent radiations and AC components corresponding to the square wave frequencies encoding the bending positions respectively. Specific signal processing on the fiber receiving end, consisting mainly of bandpass filtering and decoding, allow for the implementation of the distributed angle sensing algorithm.

Martina Gerken
Towards solution-processed top-emitting OLEDs using an phosphorescent iridium complex
Y. Murat, D. K. Subramanian, A. V. Lakshmanan, and M. Gerken
Christian-Albrechts-Universität, Kiel, Germany
This work aims to fabricate a top-emitting organic Light-emitting diode (OLED) by solution process. Research has been only focusing on evaporated top-emitting OLEDs. Printing technologies to make thin films of conjugated polymers or small molecules have been shown to be attractive to reduce the process cost. In this study, OLEDs are based on iridium complex, well-known to lead to high performance phosphorescent OLEDs by evaporation or solution process. The performances and the electroluminescence spectra measured are compared with bottom-emitting OLEDs.

Ivan Glesk
Variable weight code division multiple access system for monitoring vibration of unequally distributed points
S. Seyedzadeh¹, I. Glesk¹, F. Pour Rahimian², and Wing C. Kwong^3
1Faculty of Engineering, University of Strathclyde, Glasgow, UK
²Faculty of Engineering and Environment, Northumbria University, Newcastle, UK
³Department of Engineering, Hofstra University, Hempstead, USA
The ever-growing demand for more accurate structural health monitoring of large scale facilities such as modern high-speed railways and bridges have resulted in the development of optical sensor networks (OSN) which help eliminate the disadvantages of conventional electric sensors, the most significant of which are sensitivity to electromagnetic interferences and larger sizes. The existing fibre optic infrastructures that are implanted mainly for communication purposes are not widely used by OSNs, due to the lack of appropriate multiplexing techniques. This study proposes an optical code division multiple access (OCDMA) system for support vibration sensing of unequally distributed points. The proposed system takes the advantages of spectral amplitude encoding (SAC) technique in providing differentiated services in physical layer by varying code weights. Simulation results monitoring three vibration sensor nodes with different distances are presented in the paper. The simulation and mathematical analysis indicate the suitability and simple implementation of the proposed system for supporting vibration sensing with high accuracy.

Ramon Herrero
Structured meta-mirrors for beam spatial filtering
R. Herrero¹, Pei-Yu Wang², M. Botey¹, Yu-Chieh Cheng², and K. Staliunas^1,3
1Departament de Física, Universitat Politècnica de Catalunya, Spain
²Taipei University, Taiwan
‎³Institució Catalana de Reserca i Estudis Avançats (ICREA), Spain
The work presents optical spatial filtering in reflection based on translationally invariant meta-mirrors. The meta-structure is generated by a thin grating presenting a transverse modulation of the refraction index on the sub-micron scale located in front of a mirror. We analyze the angular spectrum of the reflected waves for different types of structured meta-mirrors as well as the filtering effects of these meta-structures in reflected beams. The comparison between FDTD simulations of full Maxwell equations and different approximated models allows to determine the filtering contribution from the structured cavity and from Mie resonances associated to elements generating the grating.

Mikko Huttunen
Towards efficient nonlinear plasmonic metasurfaces
M. J. Huttunen and M. Kauranen
Photonics Laboratory, Physics Unit, Tampere University, Finland
Nonlinear optical processes are important in many fields of photonics ranging from biomedical imaging to ultrashort pulse generation. Steady progress in nanophotonics and metamaterials has created a growing demand for efficient and nanoscale nonlinear optical components. However, it is difficult to answer this demand by using traditional materials, which motivates the search for alternative approaches. Nonlinear plasmonics has recently emerged as a viable solution for enabling efficient and nanoscale nonlinear optics [1]. Despite steady progress, so far achieved conversion efficiencies of plasmonic metamaterials have not yet rivalled conventional nonlinear materials. Here, we discuss our recent work to develop more efficient nonlinear plasmonic metamaterials. Focus will be on metasurfaces utilizing collective responses known as surface lattice resonances, which can be utilized to dramatically boost nonlinear responses of metasurfaces [2, 3].
[1] M. Kauranen and A. Zayats, Nonlinear plasmonics, Nat. Photonics, 6, 737–748 (2012).
[2] M. J. Huttunen, P. Rasekh, R. W. Boyd, and K. Dolgaleva, Using surface lattice resonances to engineer nonlinear optical processes in metal nanoparticle arrays, Phys. Rev. A, 97, 053817 (2018).
[3] R. Czaplicki et al., Less is more: Enhancement of second-harmonic generation from metasurfaces by reduced nanoparticle density, Nano Lett., 18, 7709–7714 (2018).

Brana Jelenković
Squeezed states of light generated by four wave mixing in potassium vapor
M. Ćurčić and B. Jelenković
Institute of Physics, Belgrade, Serbia
We will present results that demonstrate squeezed light source based on FWM in hot potassium vapor. Squeezed light with the noise level several dB below standard quantum limit is observed in the difference signal between correlated probe and conjugate beams, generated via FWM in potassium vapor. The vapor is contained in the vacuum K cell. For generating FWM we use nearly co-propagating pump and probe beam in a double Λ atomic scheme, which is similar to schemes used to demonstrate squeezing in Rb [1] and in K [2]. Squeezing in K [2] of about -1dB is much weaker them in Rb. In this work we will test if using FWM parameters, different from those in [2], one can make stronger squeezing in K. We have determined ranges of several FWM parameters that generate medium gains of probe and conjugate, and simultaneously small probe absorption [3], conditions that are known to produce maximum squeezing. Optimum values for pump and probe detuning and K vapor density for better squeezing, are different then in [2]. In the presentation we will show dependence of squeezing results on FWM parameters, present best values of squeezing in K vapor, and compare them with other results obtained in Rb and in K.
[1] C. F. McCormick, V. Boyer, E. Arimondo, and P. D. Lett, Opt. Lett., 32, 178 (2007).
[2] J. D. Swaim and R. T. Glasser, Phys. Rev. A 96, 033818 (2017).
[3] B. Zlatković, I. S. Radojičić, A. J. Krmpot, D. Arsenović, B. M. Jelenković, and M. Gharavipour, Phys. Rev. A 97, 063851.

Maria Kafesaki
Chiral metamaterials with parity-time symmetry and beyond
M. Kafesaki^1,2, I. Katsantonis^1,2, S. Droulias¹, E. N. Economou^1,3, and C. M. Soukoulis^1,4
1Foundation for Research and Technology Hellas (FORTH), Institute of Electronic Structure and Laser (IESL), Heraklion, Crete, Greece
²University of Crete, Dept. of Materials Science and Technology, Heraklion, Crete, Greece
³University of Crete, Dept. of Physics, Heraklion, Crete, Greece
⁴Ames lab and Dept. of Physics and Astronomy, Iowa State University, Ames, USA
We discuss the unique properties and possibilities associated with Parity-Time (PT) symmetric chiral metamaterials, emphasizing to the properties and response non-encountered in PT-symmetric non-chiral media. Such properties include real Hamiltonian eigenvalues without PT-symmetric eigenfunctions, unimodular scattering matrix eigenfunctions even in cases of deviations from the full PT-symmetry, etc. We discuss in detail those phenomena and the possibilities that they entail for the control of wave polarization.

Aslı Karakaş
Computational studies on linear and third-order nonlinear optical phenomena of dipolar subunits described for an octupolar system
A. Karakas¹, M. Karakaya², A. Migalska-Zalas³, T. Chtouki⁴, and H. Erguig^4
1Faculty of Sciences, Department of Physics, Selçuk University, Turkey
²Faculty of Engineering and Architecture, Department of Energy Systems, Sinop University, Turkey
³Faculty of Mathematics and Natural Sciences, Institute of Physics, J. Dlugosz University of Czestochowa, Poland
⁴Laboratory of Electrical Systems and Telecommunications, Electrical Engineering and Energy Team, University Ibn-Tofail, Kenitra, Morocco
We have computed the electric dipole moments (µ) , dispersion-free and frequency-dependent dipole polarizabilities (α) and third-order hyperpolarizabilities (γ) of dipolar subunits described for an octupolar system (1-3) utilizing time-dependent Hartree-Fock (TDHF) approach. To conceive the nonlinear optical (NLO) phenomena, the third-order susceptibilities (χ⁽³⁾) for the title structures have been also derived from the ab-initio quantum mechanical procedure (TDHF). According to the computed data on the NLO properties; the cubic hyperpolarizability and susceptibility results of 1-3 are considerably coherent with the measurement values initially produced.

Aslı Karakaş
Theoretical investigations on one-photon absorption wavelengths and first hyperpolarizabilities of dipolar subunits described for an octupolar system
A. Karakas¹, M. Karakaya², A. Migalska-Zalas³, T. Chtouki⁴, and H. Erguig^4
1Faculty of Sciences, Department of Physics, Selçuk University, Turkey
²Faculty of Engineering and Architecture, Department of Energy Systems, Sinop University, Turkey
³Faculty of Mathematics and Natural Sciences, Institute of Physics, J. Dlugosz University of Czestochowa, Poland
⁴Laboratory of Electrical Systems and Telecommunications, Electrical Engineering and Energy Team, University Ibn-Tofail, Kenitra, Morocco
The microscopic second-order nonlinear optical (NLO) phenomena of dipolar subunits described for an octupolar system have been investigated by means of calculating both dispersion-free and also frequency-dependent first hyperpolarizability (β) values from the density functional theory (DFT) and time-dependent Hartree-Fock (TDHF) approaches, respectively. We have estimated the maximum one-photon absorption (OPA) wavelengths by quantum chemical computations utilizing a configuration interaction (CI) technique for the title molecules in the UV area to be lower than 450 nm, indicating well optical transparencies to the visible beam. To find out the optical nonlinearity behaviour describing the molecular orbital structures; the highest occupied molecular orbitals (HOMOs), the lowest unoccupied molecular orbitals (LUMOs) and the HOMO-LUMO energy band gap properties belonging to the first and second frontier MOs have been computationally produced by the DFT procedure.

Andrzej Korcala
Admittance spectroscopy of organic and metalorganic complexes
A. Korcala^1,2, P. Płóciennik^1,2, M. Lougdali^1,3, and R. Anoua^1,4
1Department of Automation and Measurement Systems, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Torun, Poland
²Centre for Modern Interdisciplinary Technologies, Nicolaus Copernicus University, Torun, Poland
³Laboratory of Physics of Condensed Matter and Renewable Energy, Faculty of Sciences and Technology, Hassan II University of Casablanca, Mohammedia, Morocco
⁴Laboratory of Engineering Sciences for Energy, National School of Applied Sciences, Chouaib Doukkali University, El Jadida, Morocco
Quinoline is the basic representative of heteroaromatic compounds. Its derivatives are found in natural products. Because of their biological activity, they have found wide application in the pharmaceutical industry, agriculture and complexometric chemical analysis. Quinoline is also used in the construction of electronic components. The possibility of modifying molecular structure in relation to the function fulfilled in the element gives main benefits of using organic and metalorganic compounds in electronics. Presented work contains investigation results of electrical properties for AlQ₃ , Znq₂ and Cuq₂ thin films. Quinolines were prepared using PVD ( physical vapour deposition) technique. Resistance and capacitance of thin films were examined using admittance spectroscopy.

Vladimír Kuzmiak
Topological edge states in coupled photonic waveguides under periodic driving
V. Kuzmiak¹ and J. Petráček^2
1Institute of Photonics and Electronics of the CAS, Prague, Czech Republic
²Brno University of Technology, Czech Republic
We consider a photonic implementation of the topological Su Schrieffer-Heeger (SSH) model based on the coupled dielectric photonic waveguides to study the characteristics of topological edge states under both local and spatially periodic perturbations.

Andrei Lavrinenko
Lamellas metamaterials: Properties and potential applications
A. V. Lavrinenko¹, J. Sukham¹, E. Shkondin^1,2, O. Takayama¹, T. Repän¹, and R. Malureanu^1
1DTU Fotonik – Department of Photonics Engineering, Technical University of Denmark, Lyngby, Denmark
²DTU  Nanolab – National Center for Nano Fabrication and Characterization, Technical University of Denmark, Lyngby, Denmark
We report here on our advances in fabrication and characterization of lamellas metamaterials. Such structures can exhibit effective properties with enhanced and even extreme anisotropy. The latter case exhibits hyperbolic dispersion. Typical hyperbolic metamaterials (HMMs) consist of alternative metal/plasmonic and dielectric layers.  We have developed two types of lamellas metamaterials: planar multilayer and vertical trench structures. In the former case, we deposit ultrathin ultra-smooth gold layers with the assistance of organic material (APTMS) adhesion layer. The technology supports the stacking of such layers in a multi-periods construction with alumina spacers between gold films. While planar technology makes multilayer systems conventional nanostructures, vertical arrangement of nanolamellas requires a nontrivial fabrication processing.  In the latter case, we apply the atomic layer deposition (ALD) technique to arrange vertical alignment of layers of heavily doped ZnO or TiN, which enables us to produce hyperbolic metamaterials in the visible or near- and mid-infrared ranges. Potential applications of such structured lamellas metamaterials are illustrated with examples of surface waves propagation and sensing.

Boris Lembrikov
Light enhanced flexoelectric polarization in waveguiding structures with a smectic A liquid crystal (SALC) layer
B.I. Lembrikov, D. Ianetz, and Y. Ben-Ezra
Department of Electrical Engineering, Holon Institute of Technology, Holon, Israel
Flexoelectric effect results from the electromechanical coupling between the electric polarization and strain gradient [1]. Recently, the flexoelectricity in a metal/ferroelectric/semiconductor heterostructure has been investigated experimentally, and it has been shown that the enhanced flexoelectricity can be used in nanoscale devices [1]. In liquid crystals (LC), the flexoelectric polarization is due to the coupling between distortions of elongated molecules and electric polarization [2], [3]. Flexoelectric effects in nematic liquid crystals (NLC) and smectic A liquid crystals (SALC) had been observed experimentally [2], [4]. The flexoelectricity is linear in applied electric field, and it can be used in different optical applications such as pattern formation, bistable and multistable switching [2], [5]. Flexoelectric phenomena in SALC are more complicated as compared to NLC and cholesteric LC (CLC), and for this reason they still have not been used in applications [5]. It has been shown theoretically that in a SALC bulk sample the light induced dynamic grating of smectic layer strain generates a spatially periodic high-frequency electric field [6]. This phenomenon can be defined as an optically induced converse flexoelectric effect [5]. The spatially localized light induced smectic layer strain dynamic grating can be created in plasmonic and photonic waveguiding structures [7]-[9]. In this paper, we have shown theoretically that the spatially localized flexoelectric polarization can be created in a metal/insulator/metal (MIM) plasmonic waveguide containing a SALC core and in a Silicon-SALC photonic waveguide due to the induced smectic layer strain dynamic grating. We evaluated the localized high-frequency electric field generated by the flexoelectric polarization in the both cases. In the former case, the dynamic grating is enhanced by the mixing of surface plasmon polaritons (SPPs). In the latter case, the dynamic grating is created by the interfering photonic waveguide modes. The light induced flexoelectricity in SALC can used in flexoelectro-optic LC devices that have been based until now on NLC and CLC. Keywords: flexoelectricity, optical waveguide, smectic A liquid crystal (SALC), stimulated light scattering (SLS), surface plasmon polariton (SPP), dynamic grating
[1] Shujin Huang, Hei-Man Yau, Hyeonggeun Yu, Lu Qi, Franky So, Ji-Yan Dai, and Xiaoning Jiang. Flexoelectricity in a metal/ferroelectric/semiconductor heterostructure. AIP Advances, 8, 065321, 2018.
[2] Robert B. Meyer. Introduction to Flexoelectricity: Its Discovery and Basic Concepts. Flexoelectricity in Liquid Crystals: Theory, Experiments and Applications. Eds. A. Buka, N. Eber, Imperial College Press, London, 2013, pp. 1-8.
[3] F. Castles, S.M. Morris, and H.J. Coles. The limits of flexoelectricity in liquid crystals. AIP Advances, 1, 032120, 2011.
[4] J. Prost and P.S. Pershan. Flexoelectricity in nematic and smectic A liquid crystals. Journal of Applied Physics, 47, 2298-2312, 1976.
[5] P. Rudquist and S.T. Lagerwall. Applications of flexoelectricity. Flexoelectricity in Liquid Crystals: Theory, Experiments and Applications. Eds. A. Buka, N. Eber, Imperial College Press, London, 2013, pp. 211-247.
[6] G.F. Kventsel and B.I. Lembrikov. The four-wave mixing and the hydrodynamic excitations in smectic A liquid crystals. Molecular Crystals and Liquid Crystals, 262, pp. 591-627, 1995.
[7] B.I. Lembrikov, Y. Ben-Ezra, D. Ianetz. Metal/Insulator/Metal (MIM) plasmonic waveguide containing a smectic A liquid crystal (SALC) layer. ICTON 2017, Girona, Catalonia, Spain, paper Tu.A4.3, Jul. 2-6 2017.
[8] B.I. Lembrikov, D. Ianetz, Y. Ben-Ezra. Nonlinear optical phenomena in Silicon-Smectic A Liquid Crystal (SALC) waveguiding structures. ICTON 2018, Bucharest, Romania, paper Mo.D4.1, 1-5 Jul. 2018.
[9] B.I. Lembrikov, D. Ianetz, Y. Ben-Ezra. Nonlinear Optical Phenomena in Smectic A Liquid Crystals. Liquid Crystals – Recent Advancements in Fundamental and Device Technologies. Ed. P. K. Choudhury, IntechOpen, Croatia, 2018, pp. 131-157.

Aude Lereu
Giant field enhancement in resonant all-dielectric multi-layers: Advantages and limitations
A. L. Lereu¹, F. Lemarchand¹, M. Zerrad¹, A. Passian², and C. Amra^1
1Aix-Marseille Université, CNRS, Centrale Marseille, Institut Fresnel, Marseille, France
²Quantum Information Science, Oak Ridge National Laboratory, TN, USA
All-dielectric multilayer structures are emerging as optical components of great utility for experiments in which strong but localized fields are needed. These structures allow for an incoming field to resonantly interact with the layers in such a way as to create a giant field at the surface of the structure, where sensing, imaging, and other applications can take place. We present how we synthesize such structures to achieve optical responses with orders of magnitude field enhancements. Furthermore, we introduce and optimization method to achieve enhancements up to 10⁴. We will then present the advantages and drawbacks, and discuss the impact of the illumination bandwidths (angular divergence and spectral range). Subsequently, we will estimate the fabrication errors (in thicknesses and refractive index) over the optical response of the all-dielectric component and especially the field enhancement at the free interface. We will finally give a brief comparison with the surface plasmon resonances to evidence the assets and drawbacks for each case in the context of sensing applications.

Matthieu Loumaigne
Synthesis and characterization at the single particle level of aggregation induced emission nano-objects inside microfluidic devices
V. Colin, P. Frère, and M. Loumaigne
Moltech-Anjou, CNRS UMR 6200, University of Angers, France
Aggregation Induced Emission (AIE) is a relatively young field of research that is radically changing the way we use fluorophores for "real-life" applications. In this novel photophysical phenomenon, chromogens that are not fluorescent in solution become highly emissive in the aggregate or solid state. Consequently, aggregation is no more a threat for fluorophore based application and priors test that relied on 'turn-off' mechanisms can now be transferred to more sensitive "turn-on" detection scheme. Here we will present new results obtained on a series of small AIEgen push-pull molecules whose emission span the visible spectrum. The aggregates are synthetized and characterized inside microfluidic chips. This presentation will focus on the creation of composite aggregates with white-light emission.

Jarosław Myśliwiec
Photoisomerization and light amplification processes in push-pull molecules based systems
J. Myśliwiec, Wroclaw University of Science and Technology, Poland
Push-Pull organic molecules which contain an electron donor (D) and an electron acceptor (A) units that are covalently linked by a π-conjugated bridging group (D-π-A systems) exhibiting an intramolecular charge transfer (ICT) states have attracted considerable attention because of their possible use as organic optical and electronic functional materials with low energy-gap. Here we present experimental results of light amplification and photoinduced birefringence properties of newly synthesized simple thiophene and pyrazoline derivatives as a representative of low molecular push-pull type nonlinear chromophore [1,2].
[1] A. Szukalski, A. Miniewicz, K. Haupa, B. Przybyl, J. Janczak, A. L. Sobolewski, J. Mysliwiec, J. Phys. Chem. C, 120, 14813, (2016).
[2] A. Ayadi, A. Szukalski, A. El-Ghayoury, K. Haupa, N. Zouari, J. Mysliwiec, F. Kajzar, B. Kulyk, B. Sahraoui, Dyes and Pigments, 138, 255, (2017).

Ikhwan Noor
Perovskite solar cell using binary iodide gel polymer electrolytes
I. M. Noor¹ and A. K. Arof^2
1Physics Division, Centre of Foundation Studies for Agricultural Science, University Putra Malaysia, Serdang, Selangor, Malaysia
²Centre for Ionics University of Malaya, Department of Physics, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia
Methylammonium lead iodide (MAPbI₃) perovskite is a promoting material used nowadays as photo-sensitizer in solar photovoltaic devices due to its excellent properties and promising higher conversion efficiency up to 22%. In perovskite solar Z cells, Spiro-MeOTAD is the most common material used as hole conductor which play the role to transfer electrons from counter electrode to perovskite. However, this hole conductor materials are expensive. Thus, in this work we attempted to use gel polymer electrolyte (GPE) with redox mediator instead of Spiro-MeOTAD in perovskite solar cell. The perovskite layer was deposited using two-step solution method. GPE with varying composition of TBAI:KI was sandwiched between TiO₂/perovskite photoanode and platinum counter electrode. The power conversion efficiency (PCE) of 1.44% with short circuit current density (J_sc) of 3.72 mA cm^-2, open circuit voltage (V_oc) of 0.60 V and fill factor (FF) of 64.05% was obtained using electrolyte with composition 17.00wt.% PVA-12.52wt.% TBAI-1.39wt.% KI-1.07wt.% I₂-68.01wt.% DMF under 1 sun light illumination.

Przemysław Płóciennik
Temperature dependent conductivity of thin films perovskite obtained by PVD method
P. Płóciennik¹, A. Zawadzka¹, A. Korcala¹, K. Wiśniewski², and Z. Łukasiak^3
1Department of Automation and Measuring Systems, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Torun, Poland
²Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Torun, Poland
³Archimedes Sp. z o.o., R&D Department, Torun, Poland
Organometallic perovskites are under intense study for use in photovoltaic cells. We present investigation results of the electrical properties of the perovskites thin films. The films were grown by physical vapor deposition (PVD) technique on transparent (glass) and semiconductor (n-type silicon) substrates kept at room temperature during the deposition process. After the deposition process samples was stored in vacuum. Electrical properties such as the temperature dependent conductivity were tested using 4 point probe method the KEITHLEY 4200-scs system.

Ivan Richter
Numerical treatment of nonlocal nanoplasmonic resonant effects with periodic and aperiodic Fourier modal method
P. Kwiecien, M. Burda, and I. Richter
Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Department of Physical Electronics, Prague, Czech Republic
Currently, within our theoretical research under the Czech Science Foundation project Advanced functionalities in subwavelength photonic and plasmonic nanostructures, we investigate various complex functionalities, connected with subwavelength (SW) photonic and plasmonic (nano)structures. Based on our expertise with the development of (quasi)analytical and / or numerical methods for the analysis of the interaction of the electromagnetic field with such structures, we have recently studied advanced functionalities in such structures as 2D and 3D magnetooptic guiding structures with non-reciprocal properties (using our Magnetooptic Fourier modal method – 2D and 3D MoFMM), gain-loss guiding structures, advanced plasmonic biosensing metamaterial-based structures, waveguides with hybrid dielectric plasmonic slot waveguides with nonlinear properties, subwavelength grating waveguide Bragg narrow spectral filters, and Si waveguides with graphene modulation, and nonlocal plasmonic structures. Here, as the characteristic dimensions of subwavelength structures are scaling down, it has turned out that the local-response approximation is no longer applicable and more complex models based on the nonlocal response (or even quantum interaction), are required for explaining novel effects, e.g. blue spectral shifts of the resonances, etc. Among these approaches, the longitudinal nonlocal response description based on the linear hydrodynamic model represents the starting point. In this contribution, as an alternative (and more general) approach to (quasi)analytical techniques, based on our previous long-term experience with Fourier modal methods, we have considered and developed the extension of the rigorous coupled wave analysis (RCWA) technique capable of treating nonlocal response numerically, for more general structures. First, we have concentrated on the periodic nonlocal RCWA (in 1D and 2D case - NonLocRCWA) where we demonstrated the effects of nonlocal phenomena on plasmonic resonances. Next, we have converted the periodic algorithm to the aperiodic RCWA capable of treating isolated guiding structures (such as MIM – metal-insulator-metal waveguide) via the proper coordinate transform as the inter-period blocking mechanism. Some examples of the application will be shown and discussed.

Alexander Quandt
Solar cell simulations made easy
A. Quandt and R. Warmbier
School of Physics, NRF-DST Centre of Excellence in Strong Materials and Materials for Energy Research Group, University of the Witwatersrand, Johannesburg, South Africa
Numerical device simulations are a very powerful tool for the development of new types of highly efficient solar cells. The underlying theoretical framework describes many fundamental aspects of the complex flow of light through a photovoltaic device down to the atomic level, such that the most crucial simulation parameters can even be taken from first principles quantum mechanical simulations. But simpler approaches based on the Shockley diode equation are often sufficient to get an initial idea about the performance of a given basic material as part of a novel photovoltaic device. We discuss some of these simplified approaches and illustrate their applications, including the use of data from first principles simulations and/or experimental studies.

Christos Riziotis
Engineering photonic structures and functional optical materials: from structural health monitoring to biomedical applications
C. Riziotis, National Hellenic Research Foundation, Athens, Greece
The talk will cover recent activities of photonics engineering at NHRF towards the development of customized structures and devices for various demanding and emerging applications. Theoretical design and modeling issues together with experimental implementation of devices by laser writing & micromachining will be covered. Photonic platforms such as polymer optical fibers, silica or specialty fibers, plasmonic and resonating structures, functionalized by nanostructured materials will be presented as examples of a wide range customized solutions for Structural Health Monitoring, industrial predictive maintenance, defense systems and biomedical applications.

Ahmad Samsudin
A novel approaches an enhancement on electrochemical properties of polysaccharide biopolymer as polymer electrolytes for application in electrical double layer capacitor
M. A. Saadiah^1,3_, Y. Nagao², and A. S. Samsudin^3
1Department of Chemistry, Centre for Foundation Studies, International Islamic University Malaysia, Pahang, Malaysia
²School of Materials Science, Japan Advanced Institute of Science and Technology, Ishikawa, Japan
³Ionic Materials Team, Faculty of Industrial Sciences and Technology, University Malaysia Pahang, Malaysia
The science of polymer electrolytes is a highly specialized interdisciplinary field which encompasses the disciplines of electrochemistry, polymer science, organic chemistry, and inorganic chemistry. A lot of work has been made to improve the electrolytes especially using natural polymer materials which have gained more attention, owing to their being abundant in nature, friendliness to the environment, and potential as substitute for some petrochemicals. The main interest in developing electrolyte via bio-materials lies in the hope that such systems will avoid many of the problems encountered when using electrochemical devices with liquid constituents which costly along with expensive materials processing. One shows potential aspirant to act as polymer host for polymer electrolytes is carboxy methylcellulose (CMC). This due to the biocompatibility and biodegradable of their properties which attracts more attention in many application fields. The fabrication of new hybrid polymer electrolytes (HPEs) into electric double layer capacitors (EDLC) using carboxymethyl cellulose (CMC) hybrid with polyvinyl alcohol (PVA) were reported in this work. The complexes properties of HPEs were evaluated using Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrical impedance spectroscopy (EIS). The incorporation of ammonium salts in the present system lead to increase in ionic conductivity from 10^-6 to >10^-4 S/cm and shown the transference number t_H⁺ at ~ 0.4. An outstanding cycling stability over 10 000 cycles were achieved for fabricated cell as electrical double layer capacitor (EDLC) with 52.3 to 64.8 F/g, maximum energy density of 73.7 Wh/kg and high Columbic efficiency (over ~99%). This work implies that the possible practical application of the present novel electrolytes as a new candidates in the fabrication of electrochemical devices.

Silvia Schintke
Laser induced surface modification for inkjet printing and coating
O. Scheuber, E. Frau, and S. Schintke
Laboratory of Applied NanoSciences (COMATEC-LANS), Department of Industrial Technologies, HEIG-VD, University of Applied Sciences and Arts Western Switzerland, Yverdon-les-Bains, Switzerland
Lasers are nowadays widely applied in the fields of additive manufacturing and printing, e.g. in selective laser melting (SLM), selective laser sintering (SLS), stereolithography, direct write processing or laser curing of inks. We apply lasers to the fields of inkjet printing and coating and discuss examples of laser induced modifications on substrates, printed structures and thin films of transparent conductive polymers and polymer based composites.

Sebastian Schulz
Optical delay beyond the time-bandwidth limit: From pipe dream to reality
S. A. Schulz¹, D. Grassani², I. Cardea², S. J. Fabbri², J. Upham³, R. W. Boyd³, K. L. Tsakmakidis⁴, and C.-S. Brès^2
1SUPA, School of Physics and Astronomy, University of St Andrews, UK
²The Photonic Systems Laboratory, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland
³Department of Physics, University of Ottawa, Canada
⁴Department of Solid State Physics, National and Kapodistrian University of Athens, Greece
All resonant systems, independent of their physical implementation have one thing in common – their bandwidth is inversely related to the decay time. A similar relation exists in all slow light systems, where the group index (and therefore the delay for a given footprint) is inversely related to the slow light bandwidth [1]. Therefore, we can either store a broad signal for a short time, or a narrow signal for a long time, but we cannot store a broad range of frequencies for a long time. To complicate matters further, the current state-of-the-art solution, a long fibre or spiral waveguide, is not tunable and can only provide a predetermined optical delay. Here we discuss our recent work on non-reciprocal optical systems, which are not constrained by the delay-bandwidth limit [2,3]. We show that large, broadband optical delay is not a pipe dream and is achievable with current optical technology. We discuss the underlying physics of delay and bandwidth in non-reciprocal optical systems and present an experimental implementation, based on a figure-9 cavity, that demonstrates a delay-bandwidth product 30 times above the seemingly fundamental time-bandwidth limit of traditional systems. Furthermore, we show that the optical pulse can be released after an arbitrary number of round trips, providing the control and tunability lacking from conventional spiral waveguide systems.
[1] S. A. Schulz et al. Journal of Optics 12, 104004 (2010).
[2] K. Tsakmakidis et al. Science 356, 1260 (2017).
[3] D. Grassani et al. Frontiers in Optics/Laser Science, OSA Technical Digest, paper JTu3A.32 (2018).

Kestutis Staliunas
Non-Hermitian light management based on local Hilbert transform
K. Staliunas^1,2, W. Ahmed², M. Botey², and R. Herrero^2
1Institució Catalana de Recerca i Estudis Avancats (ICREA), Barcelona, Spain
²Departament de Física, Universitat Politècnica de Catalunya (UPC), Terrassa, Spain
We demonstrate a novel idea of non-Hermitian management of light based on a local Hilbert transform. Local Hilbert transform, a substantial modification of classical Hilbert transform designs non-Hermitian potentials generating arbitrary vector fields of directionality, with desired shapes and topologies. We derive a local Hilbert transform to systematically build such potentials, by modifying background potentials (being either regular or random, extended or localized). In particular, we explore particular directionality fields, for instance in the form of a focus to create sinks for probe fields (which could help to increase absorption at the sink), or to generate vortices in the probe fields. Physically, the proposed mechanism provide a flexible new tool for dynamically shaping and precise control over probe fields leading to novel effects in nonlinear wave dynamics, and in particular in broad area microlasers.

Ganapathi Subramania
Broadband, non-resonant platform for electric field enhancement
G. Subramania, Sandia National Laboratories, Albuquerque, NM, USA
Performance in several photonics applications such as detection, sensing, light emission and non-linearity enhancement can be substantially improved by electric field enhancement and efficient light funneling into deep subwavelength channels. Phenomena such as structural surface plasmon resonance and extraordinary optical transmission are typically utilized to achieve this. The resonant nature of the phenomenon makes it inherently narrowband restricting its application. Broadband electric field enhancement over a large wavelength range in the mid-infrared (~ 2-10 micron) is possible using a double-grooved metallic structure (Phys. Rev. Lett. 107, 163902(2011)) as it operates non-resonantly. We will describe fabrication of the double-groove structure and its optical response when absorptive materials are introduced. The effect of broadband electric field enhancement in the optical response will be discussed.

Paweł Szroeder
Tuning the electron band structure of graphene for optoelectronics
P. Szroeder¹, I. Sahalianov², and T. Radchenko^3
1Institute of Physics, Kazimierz Wielki University, Bydgoszcz, Poland
²Laboratory of Organic Electronics, Department of Science and Technology (ITN), Linköping University, Norrköping, Sweden
³G. V. Kurdyumov Institute for Metal Physics of the N.A.S. of Ukraine, Kyiv, Ukraine
Graphene, a conjugated sp2 carbon sheet arranged in a two-dimensional honeycomb-like lattice, shows the unique electronic structure in which conical shaped π-electron conduction and valence bands meet at the Dirac point. The properties of graphene are largely controlled by the Fermi level (chemical potential) and the density of π-electron states, which can be used for tuning graphene to specific optoelectronic and electrochemical applications. We report a computational study of the electron states and catalytic activity of graphene, which comprises the influence of uniaxial strain, covalently bonded moieties, charged ions at graphene surface, positively charged impurities located between graphene layer and substrate, and magnetic field perpendicular to graphene layers.

Rolandas Tomašiūnas
ALD oxides for GaN interfaces: A comparative view on the flat band
R. Tomašiūnas¹, I. Reklaitis¹, E. Radiunas, G. Juška¹, R. Ritasalo², T. Pilvi², M. Mandl³, S. Taeger³, and M. Strassburg^3
1Institute of Photonics and Nanotechnology, Vilnius University, Lithuania
²Picosun Oy, Espoo, Finland
³OSRAM Opto Semiconductors GmbH, Regensburg, Germany
We have deposited a series of ALD oxides HfO₂, ZrO₂, Ta₂O₅, Y₂O₃, SiO₂, Al₂O₃ within same reactor and prepared as GaN-MOS structure. A comprehensible diverse distribution of flat-band voltage depending on two different deposition temperatures 100-125°C and 250-300°C, and oxidant H₂O or O₃ was obtained. At zero gate voltage and under unstressed condition we have observed a qualitative feature demonstrating different dependence of the net fixed charge in the oxide or/and at the interface with the deposition temperature, namely, an increase of positive charge for oxidant water oxide and an increase of negative charge for oxidant ozone oxide. Best interface quality, least charge only slightly influenced by the deposition temperature, we have observed for the ZrO₂/H₂O (oxide/oxidant). Instead, highest deposition temperature dependence we have observed for the Al₂O₃/H₂O.

Krzysztof Wiśniewski
Studies of the spectroscopic properties of lead-gallium oxyfluoride (LGOF) glasses and glass-ceramics activated by Er³⁺ and Er³⁺/Yb³⁺ ions
K. Wiśniewski¹, M. Środa², A. Marczewska², and C. Koepke^1
1Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Torun, Poland
²Faculty of Material Science and Ceramics, AGH University of Science and Technology, Krakow, Poland
Lead-gallium glasses, due to the absence of typical glass-forming components, are characterized by an increased tendency to crystallization. Despite this, they are interesting materials due to a shift of IR absorption edge up to 6-7 μm. Spectroscopic properties of Er and Er-Yb doped lead-gallium glasses are investigated at low and room temperature in the near infrared region between 800 and 1800 nm. Received results are discussed base on transitions originating from the crystal filed splitting ⁴I_15/2 and ⁴I_13/2 levels.

Carmen Vázquez Garcia
Very localized temperature measurements and applications using optical fiber pyrometers
C. Vázquez¹, A. Nuñez², A. Tapetado¹, and H. Miguélez^2
1Electronics Technology Department, Universidad Carlos III de Madrid, Leganés, Spain
²Mechanical Engineering Department, Universidad Carlos III de Madrid, Leganés, Spain
Recent developments in optical fiber pyrometers providing high spatial resolution and techniques to avoid noise influence will be described in different scenarios.

Stephanos Yerolatsitis
Developing novel fibres for endoscopic imaging and sensing
S. Yerolatsitis, H. A. C. Wood, F. Yu, M. G. Tanner, S. McAughtrie, H. Fleming, C. J. Campbell, T.A. Birks, J. C. Knight, and J. M. Stone
University of Bath, UK
We are developing the next generation of optical fibres for imaging and sensing in the distal lung. The imaging fibre bundle is fabricated from cost effective OM1 PCVD graded index preforms made for the telecommunications market. While being cost effective, the performance of the image bundle is shown to be comparable to the current state-of-the-art commercial products, making it possible to be used in single use, disposable endoscopes. In addition, we are developing negative-curvature fibres, which exhibit ultra‐low silica Raman background. Measuring Raman spectra through an optical fibre is usually complicated by the high intrinsic Raman scatter of the fibre material. Common solutions such as the use of multiple fibres and distal optics are complex and bulky. The single hollow core negative curvature fibre is used for Raman and surface enhanced Raman spectroscopy sensing with no distal optics, while showing a 1000x background reduction compared to conventional fibres.

Anna Zawadzka
Photophysical properties of metal halide perovskite thin films
A. Zawadzka^1,2, M. Majranowska^1,2, P. Płóciennik^1,2, A. Korcala^1,2, and K. Wiśniewski^3
1Department of Automation and Measurement Systems, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Torun, Poland
²Centre for Modern Interdisciplinary Technologies, Nicolaus Copernicus University, Torun, Poland
³Institute of physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Torun, Poland
Hybrid organic-inorganic halide perovskites have become the most promising materials in the field of photovoltaics. In just four years the power conversion efficiency of solar cells based on hybrid perovskites has rapidly increased from an initial promising value of 9% to over 22%. Their extraordinary properties, including high carrier mobilities, low carrier recombination rates, and the tunable spectral absorption range are attributed to the unique electronic properties of these materials. The application field of hybrid perovskites has quickly expanded in terms of types of materials by substituting one or more of the organic or inorganic ions in one of the most studied perovskites, to obtain the metal halide perovskites AMX₃. This work contains investigation results of the structural and optical properties of the AMX₃ perovskites thin films. Organic-inorganic AMX₃ halide perovskites containing methylammonium lead iodide (CH₃NH₃PbI₃) and methylammonium lead chloride (CH₃NH₃PbCl₃) thin films will use for experimental investigations.

TP invited presentations:

Wolfgang Freude
Silicon photonics for coherent terahertz generation and detection
W. Freude¹, T. Harter¹, S. Muehlbrandt¹, S. Ummethala¹, S. Nellen², L. Hahn¹, S. Randel¹, and C. Koos^1
1Karlsruhe Institute of Technology (KIT-IPQ, KIT-IMT), Karlsruhe, Germany
²Fraunhofer Institute for Telecommunications Heinrich Hertz (HHI), Berlin, Germany
Silicon-plasmonic internal photoemission devices (PIPED) can act as photomixers for generating terahertz frequency carriers (T-waves) in transmitters (Tx), or function as receivers (Rx) for coherently downconverting T-wave signals to the baseband. In a first demonstration we monolithically integrate a Tx and a Rx on a silicon chip. A co-integrated transmission line connects both components.

Goran Isić
Terahertz modulation by Schottky junction in metal-semiconductor-metal microcavities
G. Isić^1,2, G. Sinatkas³, D. C. Zografopoulos⁴, B. Vasić¹, A. Ferraro⁴, R. Beccherelli⁴, E. E. Kriezis³, and M. Belić^2
1Graphene Laboratory of Center for Solid State Physics and New Materials, Institute of Physics Belgrade, University of Belgrade, Serbia
²Texas A&M University at Qatar, Doha, Qatar
³School of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Greece
⁴Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi, Rome, Italy
We discuss arrays of metal-semiconductor-metal cavities as electrically tunable terahertz metasurfaces. The considered device operation is based on reverse biasing the Schottky junction between top metal strips and the n-type semiconductor buried beneath. The effective Drude permittivity of the cavity array is tuned by a gate bias between the strips and a back metal reflector via changing the depletion layer thickness. Combining Maxwell equations for terahertz waves and a drift-diffusion model for the semiconductor carriers into a multiphysics framework, we show that the proposed modulation concept is promising for a large part of the terahertz spectrum.

Aleksandra Kaszubowska-Anandarajah
Optical generation of millimeter and THz signals using photonic integrated devices
P. D. Lakshmijayasimha¹, P. M. Anandarajah¹, P. Landais¹, and A. Kaszubowska-Anandarajah^2
1The School of Electronic Engineering, Dublin City University, Glasnevin, Dublin, Ireland
²CONNECT Research Centre, Dunlop Oriel House, Trinity College Dublin, Ireland
As the demand for wireless data transmission increases, there is a push towards adaptation of new spectral bands, which can provide us with the required capacity to satiate this demand. One of the main challenges faced at such extremely high frequencies is the generation and manipulation of the signals. Since the electronic approach suffers from low efficiency and high losses, the photonic generation of the mm-wave and THz signals becomes increasingly attractive. In this paper, we will demonstrate a photonically-integrated device that is used to generate an optical frequency comb (OFC), which in turn could be used for the optical generation of high-frequency signals. A complete OFC characterisation to demonstrate the performance and the limitations of the device, in terms of the frequency tuning range and the spectral quality of the generated signal, will be presented. We will also discuss methods of expanding the frequency comb in order to generate THz frequencies using the proposed method.

Igor Minin
Applications of terajet effect for terahertz photonics
I. V. Minin and O. V. Minin
Tomsk Polytechnic University, Russia
In this conference paper, we discuss some of the photonic technologies that can be effectively used in terahertz applications with enhanced capabilities, demonstrating some of our latest results. First, a photonic terajet phenomenon, which generates localized electromagnetic fields in the rear side of a mesoscale dielectric particles (both cubic and spherical shape), is applied to enhance a spatial resolution of THz imaging more than 2 times both in reflection and transmission modes. It means that, for example, by using a 100-GHz signal source 200-220-GHz-imaging resolution can be observed. Second, ultrafast all-optical THz modulation based on wavelength scaled dielectric cubic particle with refractive index contrast near and less than 2 and with graphene monolayer at the shadow surface was investigated numerically. These possibilities may be apply in integrated terahertz photonics for processing terahertz signals with high efficiency.

Mauro Pereira
Materials for nonlinear optics in the GHz-THz range
M. F. Pereira, Department of Condensed Matter Theory, Institute of Physics, Academy of Sciences of the Czech Republic, Prague, Czech Republic
This talk starts with an outline our hybrid approach combining Nonequilibrium Green's Functions (NEGF) and the Boltzmann equation for the nonlinear response of semiconductor superlattices (SSLs) at arbitrary. The nonlinearities are controllable and very good agreement has been found between theory and experiments [1-2].  The Terahertz-Mid Infrared (TERA-MIR) is relatively well understood [3-5] but more work is needed for our target frequency range and our results make a stepstone to generalize nonlinear optics concepts the GHZ-THz.  Furthermore, they deliver a numerical tool for designing materials and devices for a large number of applications for the detection of substances which have strong GHz-THz resonances.  In the second part of the talk, we address the ultimate efficiency of SSLs as frequency multipliers and their feasibility for room temperature THz radiation sources based on multiplication of GHz inputs, paving the way for a new generation of compact devices, delivering both odd and even harmonics and thus expanding the range of usual concepts for SSLs as odd-harmonic source [6].
[1] M.F. Pereira et al, Phys. Rev. B 96, 045306 (2017).
[2] M.F. Pereira et al, J. Nanophoton. 11 (4), 046022 (2017).
[3] M.F. Pereira, Opt. Quant. Electron. 47, 815 (2015).
[4] M.F. Pereira, Applied Physics Letters 109, 222102 (2016).
[5] M.F. Pereira and I.A. Faragai, Optics Express 22 (3), 3439 (2014).
[6] A. Apostolakis and M.F. Pereira, AIP Advances 9, 015022 (2019).

Edik Rafailov
Compact and tunable room temperature THz source from quantum dot based ultrafast photoconductive antennae
E. U. Rafailov, T. Gric, A. Gorodetsky, and N. Bazieva
Aston University, Birmingham, UK
Novel materials, notably quantum-dot (QD) semiconductor structures, offer the unique possibility of combining exploitable spectral broadening of both gain and absorption with ultrafast carrier dynamic properties. Thanks to these characteristics, QD-based devices have enhanced the properties of CW devices as well as the development of compact ultrashort pulse lasers and opened up new possibilities in ultrafast science and technology. In this paper we review recent progress in generation of CW and pulsed THz radiation from QD based photoconductive antennae (PCA) pumped by ultrafast and dual wavelength semiconductor lasers. By engineering the design of the QD structure, effective pump wavelengths can be tuned in the range between 0.9-1.3 μm, which is well beyond the GaAs energies, hence compact and relatively cheap ultrafast and narrow line double-wavelength semiconductor and fibre pump lasers can be used for pumping such antennae for both pulsed and CW THz generation. However, antennae possess a low coefficient of optical-to-terahertz conversion due to the carrier screening effect and low quantum efficiency. To overcome these limitations, an optical nano-antennae technique can be employed. Such nano-antennae can be used to enhance the electric field and increase the absorption cross section in the active layers of the photoconductive antenna. We present our recent results on enhancement of THz generation in QD based log-periodic PCA with silver nano-antennae embedded in the antenna gap. Our first results demonstrated that using silver spheroid nano-antennae fabricated by a relatively simple method, can increase the coefficient of optical-to-terahertz conversion up to 4 times. In conclusion the development of an ultra-compact, efficient, room temperature THz source is possible. The inclusion of multiple bandgap-engineered semiconductor materials and quantum-confined structures enables additional pump absorption energy ranges and ultrafast charge carrier dynamics, crucial in the efficient generation of THz radiation.

Anderson Sanches
A semi-analytical approach for performance evaluation of RTD-based oscillators
R. Nobrega^1,2, U. Duarte², T. Raddo³, I. Glesk⁴, A. Sanches^1,4, and M. Loiola^1
1Engineering, Modeling, and Applied Social Sciences Center, Federal University of ABC, Santo André, Brazil
²Academic Area of Electrical Engineering, Federal Institute of Minas Gerais, Formiga, Brazil
³Institute for Photonic Integration, Eindhoven University of Technology, Eindhoven, The Netherlands
⁴Faculty of Engineering, University of Strathclyde, Glasgow, UK
In this paper, it is presented a comprehensive analysis of three optoelectronic oscillators circuits based on resonant-tunneling diodes (RTD) for promising applications in terahertz frequency (THz) range. For all cases, it is investigated how each of these RTD devices performs under a wide range of the direct current (DC) voltages within the negative differential resistance region (NDR). The mathematical formalism developed here accounts for the effect of bias applied on the parameters of the reactive elements that composed the oscillators' small signal model. In this context, new expressions for evaluating the width of the depletion region of the devices are derived. Such mathematical formalism allows to make the performance analysis straightforward and show a close agreement to the device characterizations presented in the literature. Results pave the way for these RTD-based oscillators as potential candidates for Radio-over-Fiber (RoF) transmission, where higher operation frequencies will be major network requirements.

Andreas Stöhr
Photonic integrated chips for millimeter-wave and THz beam steering antennas
P. Lu, M. Steeg, T. Haddad, K. Neophytou, S. Makhlouf, S. Dülme, M. Grzeslo, V. Rymanov, and A. Stöhr
University Duisburg-Essen, Duisburg, Germany
This paper discusses the use of advantageous photonic integrated chips for beam switching antennas and beam steering antennas in the millimeter-wave and THz frequency ranges. Planar directive (up 15.4 dBi) frequency scanning leaky wave antennas (LWAs) connected to photodiodes for 5G beam steering (26 GHz and 60 GHz) with scanning angles up to 110° are reported. One and two dimensional (1D/2D) beam steering for wireless communication with multiple users as well as mobile terminal localization is demonstrated. Also, THz beam switching using lensed-assisted THz antenna arrays as well as THz beam steering using THz LWA and novel photonic integrated circuits (PICs) providing phase shift and true time delay (TTD) based optical beam forming networks are presented.

WAOR invited presentations:

José Roberto Amazonas
Guidelines to SLA modeling and establishment in heterogeneous communications networks
A. Akbari-Moghanjoughi¹, G. Santos-Boada¹, J. Solé-Pareta¹, and José Roberto de Almeida Amazonas^1,2
1Department of Computer Architecture, Technical University of Catalonia, Barcelona, Spain
²Escola Politécnica of the University of São Paulo, Brazil
The question of how to specify, provide and measure service quality for network end-users has been of utmost interest for service and network infrastructure providers and their clients as well. The Service Level Agreement (SLA) is a beneficial tool in formalizing the interrelationships resulting from a negotiation among all participating actors with the target of achieving a common comprehension concerning delivery of services, its priorities, quality, responsibilities, and other relevant parameters. A horizontal SLA is an agreement between two service-providers existing at the same architectural layer (as for example two Internet Protocol (IP) or two Optical Transport Network (OTN) domains). A vertical SLA is an agreement between two individual providers at two different architectural layers (for instance, between an optical network and the core MPLS network). A service has to be defined without ambiguity utilizing Service Level Specifications (SLS) and three information types must be described: i) The QoX metrics as well as their corresponding thresholds; ii) A method of service performance measurement; iii) Service schedule. In this work we present preliminary simulation results that enable the development of a generic methodology for SLA modeling and establishment that will lead to a win-win situation for all involved actors. As an example, we put special attention in the benefits obtained by Optical Networks operators.

Quan Pham Van
Exact algorithm for feasible optical channel path-aware routing and spectrum assignment in container-based microservices SDN control platforms
Q. Pham-van¹, S. Khebbache², Q-H. Tran², D. Verchere¹, and D. Zeghlache^1
1Nokia Bell Labs, Nozay, France
²Telecom SudParis, Evry, France
Optical networks are undergoing a massive transformation heading the open optical systems with services automation. The Software Defined Networking (SDN), Open Line System (OLS) disaggregation and standardization of data models including IETF, OpenConfig, OpenROADM, Transport-API, are the key factors driving this transformation. In this paper, we first introduce the evolution of optical networks, then we present a container-based microservices SDN control platform and explain how this optical network control platform as a service supports this evolution. Finally, we focus on the optical channel service provisioning with exact algorithms for Feasible Optical channel Path-Aware Routing and Spectrum Assignment.

Jesse Simsarian
The Yin-Yang of packet-optical transport SDN
J. Simsarian, Nokia Bell Labs, Holmdel, USA
The joint operation of packet and optical transport networks managed by a network operating system, enable applications that take advantage of multi-layer visibility. We present two experiments that demonstrate how performance metrics from the optical or packet layer can be utilized to make intelligent actions at the complementary layer. In the first experiments, error measurements from the optical layer are utilized to intelligently reroute packet services depending on their error tolerance. In the second experiments, packet congestion measurements are utilized to switch a photonic cross connect to create express data-center interconnection on the optical layer.

Luca Valcarenghi
Exploiting PDCP filtering for implementing a capacity-efficient virtual RAN recovery
F. Civerchia, K. Kondepu, F. Giannone, N. Sambo, P. Castoldi, and L. Valcarenghi
Scuola Superiore Sant'Anna, Pisa, Italy
This study proposes to jointly utilize virtual distributed unit (vDU) and central unit (vCU) hot backup and Packet Data Convergence Protocol (PDCP) filtering to shorten the fronthaul connection recovery time upon virtualized function failure and reduce the required backup capacity during normal working conditions.  Experimental results show that the proposed method achieves about three seconds fronthaul recovery time and reduces up to 95% the fronthaul backup connection capacity requirements.

Hélio Waldman
Capacity partitioning in the defragmented elastic single link
H. Waldman¹, R. C. Almeida Jr.², and R. C. Bortoletto^3
1Dept. of Communications, FEEC/Unicamp, Campinas, Brazil
²Dept. of Electronics and Systems, UFPE, Recife, PE, Brazil; 3Dept. of Computer Science, IFSP, São Paulo, Brazil
The paper discusses blocking and throughput analytical models for a single link under dynamic multi-class traffic, assuming defragmentation is used to mitigate fragmentation losses. The models are shown to generate reversible Markov chains that impart scalability to the performance analysis, including under any truncation of the chain that preserves the transition rates between all surviving states. The notion of link capacity pseudo-partitioning is then introduced, showing that it may be used to provide fairness between two classes in an adaptive, softwarizable fashion.

Elaine Wong
Investigating the traffic characteristics of emerging Tactile Internet applications
E. Wong and L. Ruan
University of Melbourne, Australia
The Tactile Internet will be centred on human-to-machine (H2M) applications in which humans (masters) and machines (slaves) collaborate to extend human skills. H2M applications necessitate stringent latency and reliability requirements, thereby limiting the allowable master-slave distance. AI-embedded cloudlets placed close to the tactile edge have been proposed to overcome this distance limitation. This paper discusses one of the key challenges in implementing AI-embedded cloudlets, and that is the lack of understanding of H2M traffic characteristics. To gain a deeper understanding of the characteristics of H2M traffic, we have recently developed a series of experiments to emulate H2M applications of differing dynamicity. In this paper, we will discuss some of the insights arising from these experiments which we hope will inform and innovate AI-embedded cloudlets.