Compact optical fiber photoacoustic gas sensor with integrated multi-pass cell

Enbo Fan; Haojie Liu; Chao Wang; Jun Ma; Bai-Ou Guan

doi:10.1016/j.pacs.2023.100524

Compact optical fiber photoacoustic gas sensor with integrated multi-pass cell

Photoacoustics. 2023 Jun 20:32:100524. doi: 10.1016/j.pacs.2023.100524. eCollection 2023 Aug.

Authors

Enbo Fan¹, Haojie Liu¹, Chao Wang², Jun Ma¹, Bai-Ou Guan¹

Affiliations

¹ Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications, Institute of Photonics Technology, Jinan University, Guangzhou 511443, China.
² The Center for Smart Sensing System, Julong College, Shenzhen Technology University, Shenzhen 518118, China.

Abstract

Optical fiber acoustic sensors with miniature size and high sensitivity are attractive to develop compact photoacoustic spectroscopy. Here, a compact photoacoustic gas sensor was demonstrated by utilizing a diaphragm-based fiber-optic Fabry-Perot cavity as both the acoustic sensor and the multipass cell. A nanoscale graphite film was used as the flexible diaphragm to increase the acoustic sensitivity of the Fabry-Perot cavity and the cavity inner surface was coated with highly-reflective Au film to form a multipass cell for amplification of the photoacoustic signal. With a laser power of 20 mW at 1532.8 nm, the sensor demonstrated a low detection limit of ∼ 50 ppb for C₂H₂ gas with an integration time of ∼ 100 s. The optical fiber photoacoustic gas sensor with a millimeter-scale diameter and ppb-level detection limit is promising for trace gas sensing in various areas including industrial process and environmental monitoring.

Keywords: Acoustic wave; Fabry-Perot cavity; Fiber-optic sensor; Multipass cell; Photoacoustic spectroscopy.