Waveguide-Integrated Mid-Infrared Photodetection using Graphene on a Scalable Chalcogenide Glass Platform

Abstract

The development of compact and fieldable mid-infrared (mid-IR) spectroscopy devices represents a critical challenge for distributed sensing with applications from gas leak detection to environmental monitoring. Recent work has focused on mid-IR photonic integrated circuit (PIC) sensing platforms and waveguide-integrated mid-IR light sources and detectors based on semiconductors such as PbTe, black phosphorus and tellurene. However, material bandgaps and reliance on SiO${}_2$ substrates limit operation to wavelengths $\hat{I}»\lesssim 4\hat{I}¼\text{m}$. Here we overcome these challenges with a chalcogenide glass-on-CaF${}_2$ PIC architecture incorporating split-gate photothermoelectric graphene photodetectors. Our design extends operation to $\hat{I}»=5.2\hat{I}¼\text{m}$ with a Johnson noise-limited noise-equivalent power of $1.1\mathrm{nW}/{\mathrm{Hz}}^{1/2}$, no fall-off in photoresponse up to $f=1\mathrm{MHz}$, and a predicted 3-dB bandwidth of $f_{3\text{dB}}>1\mathrm{GHz}$. This mid-IR PIC platform readily extends to longer wavelengths and opens the door to applications from distributed gas sensing and portable dual comb spectroscopy to weather-resilient free space optical communications.

15 pages, 11 figures