Investigation on mechanism of multiple holographic recording in photopolymers

Photopolymers have been considered as materials promising for holographic storage. The mechanism of holographic recording in photopolymers is the polymerization of monomers induced in the high intensity maxima of the holographic exposure pattern. Diffusion process caused by the gradient of active monomers leads to a compositional or refractive index change that mimics the holographic pattern, so phase gratings can be formed inside the material. The two processes of photo-polymerization and monomer diffusion affect each other, thus make the mechanism of grating formation in photopolymers more complicated than traditional holographic recording media. Models were introduced for the dynamics of single-grating formation in photopolymers taking into account spatial-dependent diffusion of monomers and time-dependent photo-polymerization rate. Intricate close-form solutions or numerical solutions were deduced from these models, which fitted well to experimental data for specific materials.