Controlled angular correlations and polarization speckle in scattering birefringent films

We present a comprehensive experimental and theoretical investigation into the generation and characterization of polarization speckles obtained through anisotropic scattering media, specifically liquid crystal elastomer (LCE) films with distinct molecular alignments. By fabricating two LCE films, one with random molecular distribution and the other with uniaxial alignment, we demonstrate the role of birefringence in modulating the polarization state of the scattered light. First of all, using polarized optical microscopy and crossed-polarizer optical measurements, we confirmed the anisotropic behavior of the aligned LCE film. Thereafter, the polarization-resolved speckle patterns generated from these films were analyzed using cross-correlation measurements, spatial intensity correlations, and degree of polarization (DOP) calculations. We show that the aligned LCE film preserves partial polarization information, leading to polarization-dependent speckle correlations, whereas the random LCE film completely scrambles the polarization state, resulting in polarization speckles. Furthermore, we quantified the spatial degree of coherence and Shannon entropy of the speckle patterns, revealing the influence of molecular alignment on the statistical properties of scattered light. Lastly, moving towards their application potential, we explored the angular memory effect in both random and aligned LCE films, demonstrating that the aligned LCE film exhibited extended angular correlations owing to its anisotropic structure. This finding highlights the potential for dynamic control over the angular memory effect, which can significantly enhance imaging resolution in scattering media. Our results provide a robust framework for understanding the interplay among molecular alignment, birefringence, and polarization in speckle generation, with implications for biomedical imaging & diagnostics, speckle manipulation through complex media, and for sensing applications.