Gas detection in a graphene based dual-mode fiber laser microcavity

Abstract

Detection with both high sensitivity and component distinguishability is the major goal of any chemical sensor. In the case of gas detection, such capability could enable wide applications ranging from environmental monitoring, medical diagnosis to explosion analysis. But it is still difficult to achieve in label-free photonic devices, which usually lacks versatile freedoms of measurement. Here, we report a scheme to generate both ≈ 100 kHz Q switching and ≈ 2.5 GHz cavity-mode laser oscillations in a graphene based D-shaped fiber microcavity. This allows us to simultaneously measure the two beat notes in the radio frequency. In this condition, we exploit our unique dual-mode gas sensing scheme, and we achieve real-time detection of two gas samples (CO2 and NH3) in mixture, with detect limit down to single nM/L in vacuum, and tens of ppb in air. Such combination of graphene optoelectronics, integrated fiber laser cavity and dual-mode heterodyne technique paves a way toward high performance chemical sensing, and provides inspirations for design of diverse 2D material optical devices.