Diffraction order-engineered polarization-dependent silicon nano-antennas metagrating for compact subtissue Mueller microscopy.

A polarization-dependent silicon nano-antennas metagrating (PSNM) is proposed for parallel polarization transformation by engineering diffraction orders, upon which a compact Mueller microscopy system is implemented for subtissue-level polarization extraction. The polarization-dependent metagrating is designed using matrix Fourier optics and nonlinear optimization with four diffraction orders described by waveplate-like Jones matrices, which is encoded by nano-antennas combining geometric and propagation phases. The measured phase delay and orientation of each diffraction order of the metagrating deviate by less than 6.7 % from the design values, and the overall diffraction efficiency reaches 70.89 % with a coefficient of variation of 0.021. A transmissive PSNM Mueller microscopy system is developed by directly embedding the metagrating into an infinity-corrected microscopic optical path, which extracts subtissue-level polarization distributions of biological sections over a 152 μm × 152 μm field of view with reduced measurement redundancy, facilitating the differentiation and staging of pathological tissues for potential stain-free diagnostic applications.