Experimental demonstration of two-photon Mueller matrix second-harmonic generation microscopy

We present the first experimental demonstration of two-photon Mueller matrix second-harmonic generation (SHG) microscopy for the extraction of representative Mueller matrices. Individual SHG images of porcine sample sets are divided into subimages, and the local nonlinear two-photon Mueller matrices (M⁽²⁾) and degree of polarization (p) are determined. Results of the two-photon Mueller matrices from different sample types and the effects of thickness on the mean p distribution per polarization basis are investigated. We find that the p distribution shape changes and an associated bimodal mean difference (μ_d) increases with thickness. Our approach has potential as a quantitative imaging technique and can be applied to other multiphoton coherent imaging modalities.