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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.
Sun et al. (Wed,) studied this question.