Highly sensitive and stable photothermal gas sensor with a hollow-core fiber Fabry-Perot cavity

We report a high performence all-fiber photothermal gas sensor with a stabilized hollow-core fiber Fabry-Perot interferometer. With 5.5-cm-long hollow-core fiber, we demonstrated acetylene detection down to 2.3 ppb with dynamic range over six orders of magnitude and <3% instability over a period of 24 hours.