2019 High-speed photonics

Graphene Photonics for Optical Communications (Invited paper)
Marco Romagnoli
Photonic Networks and Technologies Laboratory – CNIT, Pisa, Italy
e-mail: marco.romagnoli@cnit.it

ABSTRACT
Graphene is a gapless fermion material and this leads to a number of interesting electrooptical properties, one of them is the wavelength agnostic property, that is the possibility to operate devices at any wavelength.
Waveguides topped with graphene show both electro absorption and/or refraction modulation wit excellent figure of merit. Graphene is also used in photodetection and can be implemented as bolometer or Seebeck ultrafast
geometry. In the second case graphene detectors can be used in voltage mode.
Graphene is also an integrable material that results particularly compatible with silicon photonics and related materials. The wafer scale integration technology mainly require newly developed steps as graphene transfer, encapsulation and contacting. The quality of these steps determines the performance of the device.

Graphene Photonics for Optical Communications


8 x 40 Gb/s WDM Photonic Integrated Wavelength Switch Module for Optical Data Center Networks
Kristif Prifti1, Netsanet Tessema1, Xuwei Xue1, Ripalta Stabile1, Nicola Calabretta1
1 IPI Research Institute, Eindhoven University of Technology, Eindhoven – The Netherlands e-mail: k.prifti@tue.nl

ABSTRACT
We characterize the performance of a photonic integrated 1×8 WDM (8 channels Wavelength-Division Multiplexing) wavelength selective switch (WSS) module to realize a modular 8x8x8λ cross-connect switch. The module is based on SOA (Semiconductor Optical Amplifier) optical gates for nanoseconds wavelength and time switching operation. This technology enables the realization of low latency optical data center networks. Experimental measurements demonstrate a cross-talk lower than -35 dB, 11 dB/channel on chip gain and error-free operation at 40 Gb/s with limited penalty. The on chip gain and low cross-talk results presented in this study and the device proposed, being a scaled up version with double the channels of a previously demonstrated 4 x 4 modular architecture, validate the potentialities of this approach to scale up to an even larger channel number and hence port count.
Keywords: SOA (Semiconductor Optical Amplifier), PIC (Photonic Integrated Chip), DCN (Data Center Network), WSS (Wavelength Selective Switch).

8 x 40 Gb/s WDM Photonic Integrated Wavelength Switch Module for Optical Data Center Networks


First Silicon Photonics Coherent Receiver With Heterogeneously Integrated
III-V On Silicon Tunable Local Oscillator Operating At 28GBd Data Rates

Hajar Elfaiki1, Xavier Pommarede1, Christophe Caillaud1, Harry Gariah1, Dalila Make1,
Th´eo Verolet1, Karim Hassan2, Christophe Jany2, St´ephane Malhouitre2,
S´egol`ene Olivier2, Mohand Achouche1
1 III-V Lab, joint lab of Nokia, Thales & CEA, 1 A. Fresnel, 91767 Palaiseau, France
e-mail: hajar.elfaiki@3-5lab.fr
2 CEA LETI, Minatec, 17 rue des Martyrs, 38054 Grenoble, France

ABSTRACT
We demonstrated the first coherent receiver with III-V on silicon monolithic integrated local oscillator. It shows clean QPSK constellation at 28 GBd with 1:7 10􀀀4 BER, and a footprint shrunk to 2mmx 1.5 mm. The local oscillator presents a 45 nm tuning range obtained by thermally tuned Vernier filter. The compactness of the rings ensures a reduced power consumption of 200mW sufficient to span the whole tuning range. The local oscillator shows a narrow linewidth of 150 kHz compatible with high speed coherent detection.
Keywords: Silicon Photonics, Coherent Detection, III-V on Silicon Monolithic Integration, Photonic Integrated Circuits

First Silicon Photonics Coherent Receiver With Heterogeneously Integrated
III-V On Silicon Tunable Local Oscillator Operating At 28GBd Data Rates


High-speed-performing pin photodetectors with lateral silicon-germanium-silicon heterojunctions for 1.55 μm communications
D. Benedikovic1, L. Virot2, G. Aubin1, J.-M. Hartmann2, F. Amar1, B. Szelag2, B. Karakus2, C. Alonso-Ramos1, X. Le Roux1, P. Crozat1, E. Cassan1, D. Marris-Morini1, C. Baudot3, F. Boeuf3, J.-M. Fédéli2, C. Kopp2, and L. Vivien1
1Centre de Nanosciences et de Nanotechnologies, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91120 Palaiseau, France
2University Grenoble Alpes, CEA, LETI, 38054 Grenoble, France
3Technology R&D, STMicroelectronics, 38920 Crolles, France
e-mail: daniel.benedikovic@c2n.upsaclay.fr

ABSTRACT
We investigate the properties of high-speed waveguide photodetectors with hetero-structured Silicon-Germanium-Silicon junctions monolithically integrated on Silicon-on-Insulator substrates. These devices take advantage of unique integration strategy that combines butt-waveguide-coupling and lateral Silicon-Germanium-Silicon pin junctions. Fabrication is robust and fully compatible with complementary metal-oxide-semiconductor technology. The resulting devices have improved responsivity and bandwidth performances. In particular, a responsivity up to 1.2 A/W and a dark-current as low as 100 nA under 1V reverse bias are experimentally demonstrated with a set of pin photodetectors. Furthermore, fast device opto-electrical responses lead to an excellent on-chip detection capability well-suited for future high-speed link traffics up to 40 Gbps. An errorless operation is achieved for established 10 Gbps and 25 Gbps data rates, providing a power sensitivities of -13.9 dBm and -11.3 dBm with a bit-error-rate of 10-9.
Keywords: group-IVnanophotonics, silicon-on-insulator, germanium photodetectors, optical communications.

High-speed-performing pin photodetectors with lateral silicon-germanium-silicon heterojunctions for 1.55 μm communications


Optical transceiver engine based on 12 μm Silicon-on-insulator waveguides and VCSELs
Mikko Karppinen1, Mikko Harjanne1, Tapani Vehmas1, Christian Neumeyr2, Aila Sitomaniemi1, Jyrki
Ollila1, Markku Kapulainen1, Antti Tanskanen1, Päivi Heimala1, Timo Aalto1
1 VTT, PO Box 1000, (Vuorimiehentie 3, Espoo), FI-02044 VTT – Finland
2 Daimlerstr. 11d, D-85748 Garching – Germany
e-mail: Mikko.Karppinen@vtt.fi

ABSTRACT
In this paper, we report the fabrication of an optical tranceiver engine that is based on a 12μm silicon on insulator (SOI) waveguide platform and directly modulated vertical cavity surface emitting lasers (VCSELs). The main motivation for using 12 μm thick SOI waveguides is low-loss coupling to standard SM fibers with relaxed alignment tolerances. We demonstrate 25.7Gb/s operation of the complete optical interconnect link channel.
Keywords: silicon photonics, silicon-on-insulator, optical interconnect, VCSEL, hybrid integration

Optical transceiver engine based on 12 μm Silicon-on-insulator waveguides and VCSELs