Optical modulation in Ge-rich SiGe waveguides in the mid-infrared wavelength range up to 11 \xb5m

Miguel Montesinos-Ballester,Andrea Ballabio,Giovanni Isella,Joan Manel Ramirez,Qiankun Liu,Vladyslav Vakarin,Xavier Le Roux,Andrea Barzaghi,Lucas Deniel,Carlos Alonso-Ramos,Laurent Vivien,David Bouville,Delphine Marris-Morini,Jacopo Frigerio

doi:10.1038/s43246-019-0003-8

Abstract

Waveguide integrated optical modulators in the mid-infrared wavelength range are of significant interest for molecular spectroscopy. This is because on-chip synchronous detection can improve the performance of detection systems and can also be used for free-space communications where optical modulators working in atmospheric transparency windows are needed. Here we report optical modulation in a mid-infrared photonic circuit, reaching wavelengths larger than 8 µm. Optical modulation in the wavelength range from 5.5 to 11 µm is shown, relying on a broadband Ge-rich graded-SiGe platform. This demonstration experimentally confirms the free-carrier absorption effect modeling. These results pave the way towards efficient high-performance electrically-driven integrated optical modulators in the mid-infrared wavelength range.

Highlights

2, Lucas Deniel[1], Waveguide integrated optical modulators in the mid-infrared wavelength range are of significant interest for molecular spectroscopy
Spectroscopic detection systems would benefit from the development of an integrated mid-IR modulator, as detection sensitivity can be greatly enhanced via synchronous detection
Such ultra-wideband light confinement is a unique property directly related to the refractive index gradient effect and 1.5-cm-long rib waveguides have been fabricated as described in the “Methods” section

Summary

Introduction

2, Lucas Deniel[1], Waveguide integrated optical modulators in the mid-infrared wavelength range are of significant interest for molecular spectroscopy. Optical modulation in the wavelength range from 5.5 to 11 μm is shown, relying on a broadband Ge-rich graded-SiGe platform This demonstration experimentally confirms the free-carrier absorption effect modeling. These results pave the way towards efficient high-performance electrically-driven integrated optical modulators in the mid-infrared wavelength range. A large variety of high-speed optical modulators have been demonstrated using free carrier plasma dispersion effect in the nearIR wavelength range[22]. The extension of this effect to the mid-IR has been theoretically evaluated first in Si23 and in Ge24. Experimental demonstrations appear to be essential to confirm current models for the design of electrically driven mid-IR optical modulators

Methods

Results

Conclusion