Noise canceled graphene-microcavity fiber laser sensor for ultrasensitive gas detection

Abstract

Optical microcavities offer a promising platform for highly efficient light–matter interactions. Recently, the combination of microresonators and 2D materials in the nanoscale has further enriched the optoelectronics of microcavity geometries, spurring broad advances including lasers, nonlinear converters, modulators, and sensors. Here, we report the concept of compact dual-laser cogeneration in a graphene-microcavity fiber, which offers a way to cancel the optical common mode noises. Driven by a single 980 nm pump, orthogonally polarized laser lines are generated in a pair of degeneracy breaking modes. The two laser lines produce a heterodyne beat note at 118.96 MHz, with frequency noise down to 200  Hz2/Hz at 1 MHz offset, demonstrating a linewidth of 930 Hz in vacuum. This compact device enables on-line and label-free NH3 gas detection with high resolution, realizing a detection limit on a single pmol/L level, and a capability to quantitatively trace gas–graphene interactions. Such a combination of graphene optoelectronics and microcavity photonics demonstrates a novel physical paradigm for microlaser control and offers a new scheme for in situ chemical sensing.