Polarization-Resolved Speckle Technique for Rapid Non-Destructive Characterization of Macroporous Silica Thin Films

Macroporous silica thin films were synthesized via the sol-gel method to elucidate the relationship between pore structure and the degree of polarization of light (DoP). The films were characterized by scanning electron microscopy (SEM) to determine their mean pore size and surface porosity, while polarization-resolved speckle imaging was employed to evaluate the degree of polarization and its distribution on the Poincaré sphere. The results show that surface porosity is a key structural parameter governing the DoP, with increasing values leading to enhanced scattering and a progressive isotropization of the polarization-state distributions. Poincaré sphere mapping further reveals distinct scattering regimes and polarization-conversion pathways, providing insights that are not accessible with conventional optical measurements. Overall, these findings show that speckle imaging is a rapid, cost-effective, and non-destructive approach to probing structural and optical anisotropies in porous materials, with direct relevance to systems where pore accessibility dictates performance, including liquid-crystal devices, photochromic coatings, and other nanostructured photonic platforms.