Fig. 1. Frequency response of photoacoustic cell in SF₆ and N₂ background

Fig. 2. Diagram of the simulated reflected light path

Fig. 3. Schematic of simulation and experimental adjustment of spot distribution

Fig. 4. Selection of H₂S absorption lines

Fig. 5. Schematic of the photoacoustic spectroscopy trace gas detection system

Fig. 6. The relationship between photoacoustic signal amplitude and modulation current

Fig. 7. Resonance frequencies of multi-pass cell under different background gases

Fig. 8. Single and multiple reflection photoacoustic signal amplitudes

Fig. 9. Relationship between photoacoustic response and H₂S/SF₆ mixed gas concentration

Fig. 10. Allan-Werle deviation analysis results