Polarized photoacoustic microscopy for vectorial-absorption-based anisotropy detection

We proposed a polarized photoacoustic microscopy (PPAM) for quantitative detection of a target’s microscopic anisotropy based on the vectorial optical absorption by applying four linearly polarized laser beams as excitation sources. Compared with conventional photoacoustic microscopy that treats targets as isotropic absorbers, the PPAM allows us to quantitatively detect the target’s anisotropic features beyond optical absorption with a newly-proposed parameter valued between 0 and 1. The feasibility of the method was validated by dichroic phantoms. The dichroic compound eyes of mantis shrimps were imaged in situ to demonstrate its capability for quantitative 3D biological imaging. The PPAM method provides an effective and straightforward strategy for tissue polarimetry, prefiguring great potential for biological imaging and material inspection.