Brillouin lasers in a graphene microresonator for multispecies and individual gas molecule detection

Abstract

Optical microcavities offer a promising platform for highly efficient light–matter interactions. Recently, the combination of microresonators and 2D materials in nanoscale has further enriched the optoelectronics of the microcavity geometries, spurring broad advances ranging from lasers, nonlinear converters, modulators to sensors. Here, we report the concept of a Brillouin laser sensor, by depositing graphene on an over-modal microsphere. Driven by a single continuous-wave pump at 1550 nm, multiple Brillouin lasers from distinct mode families are co-generated in a single device. The Brillouin lasers excited in the high Q cavity produce heterodyne beating notes with phase noise down to −161 dBc/Hz at 1 MHz offset, not only enabling label-freely identifiable detection of multispecies gas molecules adsorbed on the graphene in situ but also rendering it possible to trace individual molecules. Such a combination of graphene optoelectronics and Brillouin lasers in microcavities demonstrates a novel physical paradigm and offers insights into powerful tools for fast and precise optical sensing.