Photorefractive trapping and the correlation between recording and erasure dynamics in a polymer composite

Summary form only given. There exists no consensus about the nature of trapping sites in photorefractive polymer composites. Many authors have suggested that microscopic inhomogeneities and structural deformations are the trap sites. In this case, optical de-trapping is a different process from photogeneration which, in contrast to photorefractive crystals, is recognized to occur at sensitizer molecules in polymer composites. However, we present evidence that the processes of charge generation and optical de-trapping are the same in polymers i.e. both involve excitation of sensitizer molecules. Using a degenerate four wave-mixing experiment, holographic contrast growth and erasure curves were measured for a variety of material compositions and under a wide range of experimental conditions.