Highly sensitive H2S-LITES sensor with 80 m fiber-coupled multi-pass cell based on optical path multiplexing technology
Haiyue Sun, Ying He, Shunda Qiao, Chu Zhang, Yufei Ma
Abstract
This paper presented a highly sensitive light-induced thermoelastic spectroscopy (LITES) sensor for detecting hydrogen sulfide (H₂S) gas. Optical path multiplexing (OPM) technology was implemented within the fiber-coupled multi-pass cell (MPC) to realize ~ 80 m gas absorption optical path length (OPL), compensating the weak absorption coefficient of H 2 S in the near-infrared band. A circle-head quartz tuning fork (QTF) with resonant frequency of ~ 9.5 kHz was adopted in the H₂S-LITES sensor to enhance the energy accumulation time and the detection ability. Compared with commercial QTF, signal-to-noise ratio (SNR) based on circle-head QTF was improved by a factor of 3.36 times. Minimum detection limit (MDL) for H 2 S detection was measured to be 238.8 ppb. When the integration time of the system was increased to 250 s, the MDL could be improved to 19.8 ppb.