Fig. 1. The production process of photoacoustic signal

Fig. 2. The gas detection system of photoacoustic spectrum

Fig. 3. Gas detection system with incoherent light source

Fig. 4. Vehicle borne photoacoustic spectrum gas detection system

Fig. 5. Fiber laser photoacoustic spectrometer

Fig. 6. Multi-channel gas detection system with DFB laser

Fig. 7. Time division multiplexing multi-gas sensor with five QCLs

Fig. 8. Resonant cavity parallel system

Fig. 9. Structure diagram of multi-channel photoacoustic cell

Fig. 10. Gas detection system of multi-channel photoacoustic cell

Fig. 11. Schematic of fiber acoustic sensor detection unit

Fig. 12. Schematic of cantilever enhanced photoacoustic spectroscopy detector

Fig. 13. Structure diagram of fiber F-P cantilever sensing

Fig. 14. Schematic diagram of quartz enhanced photoacoustic spectroscopic microphone
(a): On-beam configurations; (b): Off-beam configurations

Fig. 15. Gas detection system of quartz enhanced photoacoustic spectroscopy