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Appl. Sci. 2018, 8(7), 1154;

Wideband Ge-Rich SiGe Polarization-Insensitive Waveguides for Mid-Infrared Free-Space Communications

Centre de Nanosciences et de Nanotechnologies (C2N), Université Paris Saclay, Université Paris Sud, CNRS, 91405 Orsay, France
L-NESS, Dipartimento di Fisica del Politecnico di Milano, Polo di Como, Via Anzani 42, I 22100 Como, Italy
National Research Council, Ottawa, ON K1A 0R6, Canada
Department of Electronics, Carleton University, 1125 Colonel by Dr., Ottawa, ON K1S 5B6, Canada
Author to whom correspondence should be addressed.
Received: 19 June 2018 / Revised: 7 July 2018 / Accepted: 12 July 2018 / Published: 16 July 2018
(This article belongs to the Special Issue Silicon Photonics – Emerging Devices and Applications)
Full-Text   |   PDF [2134 KB, uploaded 16 July 2018]   |  


The recent development of quantum cascade lasers, with room-temperature emission in the mid-infrared range, opened new opportunities for the implementation of ultra-wideband communication systems. Specifically, the mid-infrared atmospheric transparency windows, comprising wavelengths between 3–5 µm and 8–14 µm, have great potential for free-space communications, as they provide a wide unregulated spectrum with low Mie and Rayleigh scattering and reduced background noise. Despite the great efforts devoted to the development of mid-infrared sources and detectors, little attention is dedicated to the management of polarization for signal processing. In this work, we used Ge-rich SiGe alloys to build a wideband and polarization-insensitive mid-infrared photonic platform. We showed that the gradual index change in the SiGe alloys enabled the design of waveguides with remarkably low birefringence, below 2 × 10−4, over ultra-wide wavelength ranges within both atmospheric transparency windows, near wavelengths of 3.5 µm and 9 µm. We also report on the design of a polarization-independent multimode interference device achieving efficient power splitting in an unprecedented 4.5-µm bandwidth at around 10-µm wavelength. The ultra-wideband polarization-insensitive building blocks presented here pave the way for the development of high-performance on-chip photonic circuits for next-generation mid-infrared free-space communication systems. View Full-Text
Keywords: photonic integrated circuits; mid-infrared; polarization-insensitive photonic integrated circuits; mid-infrared; polarization-insensitive

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Vakarin, V.; Ramírez, J.M.; Frigerio, J.; Liu, Q.; Ballabio, A.; Le Roux, X.; Alonso-Ramos, C.; Isella, G.; Cheben, P.; N. Ye, W.; Vivien, L.; Marris-Morini, D. Wideband Ge-Rich SiGe Polarization-Insensitive Waveguides for Mid-Infrared Free-Space Communications. Appl. Sci. 2018, 8, 1154.

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