Fig. 1. Principle of photoacoustic spectroscopy

Fig. 2. Structure of synaptic photoacoustic cell

Fig. 3. Evaluation of two-dimensional mesh quality

Fig. 4. Simulation of the first eight acoustic modes

Fig. 5. Influence of various factors on photoacoustic cell performance

Fig. 6. Results of Box-Behnken experimental design

Fig. 7. The flowchart for the parameter optimization method of the hetero-shaped photoacoustic cell combining DOE with the NSGA-II

Fig. 8. Distribution of pareto optimal frontier

Fig. 9. Comparative analysis of acoustic field characteristics between the cylindrical and the synaptic photoacoustic cell

Fig. 10. Comparative analysis of flow field characteristics between the cylindrical and the synaptic photoacoustic cell

Fig. 11. Synaptic photoacoustic cell physical image

Fig. 12. Composition of the photoacoustic spectroscopy system

Fig. 13. Frequency response

Fig. 14. Dynamic response test results

Fig. 15. Distribution of photoacoustic signal over 5 hours