Effects in reconstruction of diffraction gratings multiplexed in acrylamide photopolymers

In this study we focus on the properties of acrylamide photopolymer layers about 1 mm thick with hydrofilic binder of polyvinyl alcohol and yellowish eosin as dye. We consider peristrophic multiplexing. Note the differences in the reconstruction step between the next two peristrophic multiplexing schemes: rotation axis parallel and rotation axis perpendicular to the hologram media. In the first case (parallel) a very thick media allows for a high storage density and a highly selective individual hologram reconstruction thanks to the Bragg angular selectivity. In the second case (perpendicular), an additional optical system is necessary to separate the various simultaneous holograms reconstructed. We show experimental evidence for the two schemes. We analyze the behaviour of the material when multiplexing diffraction gratings using peristrophic multiplexing. In the reconstruction step we observe differences, between the various multiplexed holograms, in their angular response shape. We consider that this is due to polymer diffusion in exposed areas or to the dye concentration variation with registered holograms number, because xantene dyes are bleached at the initiation step of radical polymerization reaction. The photopolymer composition is an important factor to be taken into account when single or multiple holograms are registered. The differences in both cases are considered in this work.This work was supported by the "Dirección General de Investigación y Transferencia Tecnológica", Generalitat Valenciana, Spain (projects GV04A/547 and GV04A/565)