Ultra-sensitive gas detection using noise-canceled graphene-microcavity-based fiber laser sensor

By combining the dual laser co-generation-based common noise canceling effect and the graphene-based sensitivity enhancement, we demonstrate an in-microcavity fiber laser sensor. We use a single 980 nm pump that generates an orthogonally polarized laser pair in degeneracy-breaking modes, producing a heterodyne beat signal at 118.96 MHz with a linewidth of 930 Hz in vacuum. The frequency noise is reduced to 200 Hz²/Hz at a 1 MHz offset. This compact device enables ultrasensitive ammonia detection, achieving a detection limit of 2 pMol/L in vacuum and 0.01 ppb in air. Such integration of graphene optoelectronics and microcavity photonics on fiber offers a new approach for micro-laser control and in-situ optical fiber sensing.