TEMPERATURE-INDUCED CHANGES IN PHOTOPOLYMER VOLUME HOLOGRAMS

Temperature-induced distortions of plane-wave holographic gratings rec orded in low glass transition temperature (T-g similar to 26 degrees C ) photopolymer media were measured. Changes in temperature affect the refractive index and dimensions of photopolymer materials, thereby rot ating the angular Bragg selectivity of recorded volume holograms. From temperature-dependent measurements on a set of angularly multiplexed holograms, the out-of-plane coefficient of thermal expansion of a thin photopolymer film constrained between two rigid glass substrates is f ound to be 500 ppm/degrees C; These experiments suggest that the tempe rature sensitivity of photopolymer volume holograms may limit their us e in many applications. (C) 1998 American Institute of Physics. [S0003 -6951(98)00636-6].