Birefringence Mapping of Diffractive Optical Elements on Gold-Doped Azopolymer Nanocomposites by Polarization Digital Holographic Microscopy

This study investigates the birefringence behavior of diffractive optical elements (DOEs) recorded on gold-doped photosensitive azopolymer nanocomposite thin films, employing polarization digital holographic microscopy (PDHM) in combination with Jones transmission matrix analysis. Nanocomposite films were fabricated from a toluene solution of doped carbazole-based photosensitive azopolymer with a number of varying concentrations of gold nanoparticles (AuNPs). DOEs were directly inscribed via polarization-sensitive holographic recording, and their birefringent properties were mapped in three dimensions using a custom-built PDHM system equipped with a Kiralux polarization camera. The reconstructed phase and amplitude data were further analyzed through spatially resolved Jones matrix calculations by MATLAB code, enabling a quantitative evaluation of local birefringence parameters, such as retardance and optical axis orientation. Results demonstrate a clear dependency of birefringence on AuNP concentration, with higher doping levels significantly enhancing molecular reorientation efficiency and induced anisotropy during the holographic recording process. Jones transmission matrix analysis revealed distinct polarization modulation patterns across the recorded DOEs. The integration of PDHM with Jones matrix formalism offers a robust and non-invasive methodology for detailed birefringence characterization in advanced photoactive nanocomposites. This approach not only advances the understanding of the optical response in AuNP-doped azopolymers but also supports the development of customizable, polarization-sensitive diffractive components for modern photonic applications.