Analysis of the photo-absorptive behavior of two different photosensitizers in a photopolymer material

Photopolymer materials are practical materials for use as holographic recording media. To further develop such materials, a deeper understanding of the photochemical mechanisms present during the formation of holographic gratings in these materials has become ever more crucial. This is especially true of the photoinitiation process, which has already received much attention in the literature. Typically the absorption mechanism varies with exposure time. This has been previously investigated in association with several effects taking place during recording. Since holographic data storage requires multiple sequential short exposures, it is necessary to verify the temporal change in photosensitizer concentration. Postexposure effects have also been discussed in the literature, however, such studies do not include effects such as photosensitizer recovery and bleaching. We report on experimental results and theoretical analysis of the recovery and bleaching mechanisms, which arise during exposure and postexposure for two different types of photosensitizers, methylene blue and erythrosine B in a polyvinylalcohol–acrylamide based photopolymer material.