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

TL;DR

This paper presents a scalable mid-infrared photodetector platform using graphene integrated on a chalcogenide glass waveguide, achieving operation at 5.2 micrometers and promising for various sensing and communication applications.

Contribution

It introduces a novel chalcogenide glass-on-CaF2 PIC architecture with split-gate graphene photodetectors that extend mid-IR detection beyond 4 micrometers.

Findings

Operation at 5.2 micrometers wavelength.

Johnson noise-limited noise-equivalent power of 1.1 nW/Hz^{1/2}.

No photoresponse fall-off up to 1 MHz, with a predicted bandwidth over 1 GHz.

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 $\lambda\lesssim4\,\mu\textrm{m}$. 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 $\lambda=5.2\,\mu\textrm{m}$ 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 $f_{3\textrm{dB}}>1\,\mathrm{GHz}$. 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.