Temperature-induced changes in photopolymer volume holograms

Temperature-induced distortions of plane-wave holographic gratings recorded in low glass transition temperature (Tg∼26 °C) photopolymer media were measured. Changes in temperature affect the refractive index and dimensions of photopolymer materials, thereby rotating 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 found to be 500 ppm/°C. These experiments suggest that the temperature sensitivity of photopolymer volume holograms may limit their use in many applications.