Super-resolution photoacoustic imaging based on saturation difference of transient absorption

As a label-free, non-invasive, and high-contrast imaging technology, photoacoustic microscopy (PAM) is widely used in biomedical science. However, due to the restriction of diffraction limit, the optical resolution of PAM has not been effectively improved. In this paper, in order to break the diffraction limit, a patterned competition based on saturable transient absorption effect is introduced to realize the super-resolution imaging into the conventional photoacoustic microscopy. We have provided a physical model of photoacoustic microscopy based on transient absorption saturation difference (TASD-PAM) and verified its effectiveness by analyzing the photophysical properties of our sample and imaging it with a sub-diffraction lateral resolution. Compared to reported pump-probe microscopy, which is based on stimulated emission depletion or ground-state depletion process, our method can realize the label-free super-resolution imaging of dark materials that cannot emit fluorescence. This technique enables observing the microstructure of dark materials in a way that defies the diffraction limit, which will expand the application range of photoacoustic microscopy and open up a new way for super-resolution imaging.