Linear response deviations in photopolymers

Abstract

In holographic recording photopolymers the diffraction efficiency develops according to Kogelnik expression during hologram recording stage. In the ideal situation, the curve of diffraction efficiency versus energetic exposure has a linear zone, although it is usual to find examples of deviations to this behavior. In this investigation we study different cases in which there are deviations to ideal behavior, proposing different hypothesis in order to explain the situations that can be experimentally obtained. The more important deviation experimentally observed is when the first maximum is lower than the second one in the diffraction efficiency versus exposure curve during recording. A main hypothesis is presented, which is related to the dye concentration into the layer and the molecular weight of the polymer chains generated in the polymerization process.