A quartz‑enhanced photoacoustic sensor for H2S trace‑gas detection at 2.6 μm

We report on the realization of a quartz-enhanced photoacoustic (QEPAS) sensor for measurement of H2S gas traces. A distributed feedback diode laser working at 2.64 µm wavelength has been coupled to an acoustic detection module composed of a quartz tuning fork and a micro-resonator system, and the QEPAS signal has been optimized in terms of gas sample pressure and laser frequency modulation depth. The sensor shows a very good linearity with respect to the H2S concentration. We performed an Allan–Werle variance analysis to investigate the sensor long-term stability, and we reached a detection limit of four parts per million for 1-s integration time and 500 parts per billion in 60-s integration time. The realized QEPAS sensor represents a good compromise between performance and handiness, in view of a fully portable device.