Experimental study of photoacoustic signals from absorbers with multilayer absorption distribution

Photoacoustic imaging is a promising non-invasive biomedical imaging technology that has developed rapidly in recent years. It has high contrast and resolution, and can be used to locate blood vessels and tumors in biological tissues through photoacoustic signals. It is generally believed that the amplitude of the photoacoustic signal is proportional to the absorption coefficient of the tissue, but it is found in the experiment that for the uniform absorber, the total signal is generated at the absorption boundary, and the photoacoustic signal in the middle of the absorber is very low, even if the absorption coefficient of the absorber is very large. In this paper, through experiments and comsol software simulation, it is found that the size of the photoacoustic signal generation should be related to the change of the absorption gradient of pulsed light. This finding is of great significance for the photoacoustic signal and its photoacoustic image reconstruction of complex absorbers with multi-layer absorption distribution.