Photoacoustic spectroscopy (PAS) is an effective gas-sensing technique for environmental monitoring, industrial process control, and safety-related detection because of its high sensitivity and compact detection scheme. For the detection of different gas species, conventional PAS systems often rely on several wavelength-specific lasers to excite the corresponding gas absorption lines. In this work, we demonstrate a compact, single-longitudinal-mode, widely tunable actively Q-switched solid-state laser as an excitation source for PAS multi-gas sensing. The laser uses a Tm:YAP crystal as the gain medium and operates near 1950 nm. A tuning range of 100 nm is achieved, which covers the absorption features of seven gas species (CH 4 , C 2 H 2 , CO 2 , H 2 O, NH 3 , N 2 O, and H 2 S). The laser also delivers a highest peak power of up to 27 W and an adjustable repetition rate. This tunable pulse repetition rate allows the pulse repetition rate to be matched to the acoustic resonance frequency of the PAS cell without an external intensity modulator. The laser was used for PAS detection of N 2 O, CH 4 , and C 2 H 2 , with the lowest detection limits reaching the ppm level. These results show that the proposed laser can replace multiple wavelength-fixed sources in conventional PAS systems and offers a compact, simple, and highly sensitive solution for PAS multi-species gas detection. This work demonstrates a proof-of-concept multi-gas PAS platform based on a widely tunable, stable single-longitudinal-mode pulsed solid-state laser.
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Huang et al. (2026) studied this question.