Light-induced thermoelastic sensor for ppb-level H2S detection in a SF6 gas matrices exploiting a mini-multi-pass cell and quartz tuning fork photodetector
Bo Sun, Pietro Patimisco, Angelo Sampaolo, Andrea Zifarelli, Vincenzo Spagnolo, Hongpeng Wu, Lei Dong
Abstract
We present an optical sensor based on light-induced thermoelastic spectroscopy for the detection of hydrogen sulfide (H2S) in sulfur hexafluoride (SF6). The sensor incorporates a compact multi-pass cell measuring 6 cm × 4 cm × 4 cm and utilizes a quartz tuning fork (QTF) photodetector. A 1.58 μm near-infrared distributed feedback (DFB) laser with an optical power of 30 mW serves as the excitation source. The sensor achieved a minimum detection limit (MDL) of ~300 ppb at an integration time of 300 ms, corresponding to a normalized noise equivalent absorption coefficient (NNEA) of 3.96×10-9 W·cm-1·Hz-1/2. By extending the integration time to 100 s, the MDL can be reduced to ~25 ppb. The sensor exhibits a response time of ∼1 min for a gas flow rate of 70 sccm.