EXPERIMENTAL METHOD FOR DETERMINATION OF SHRINKAGE DIRECRION DURING HOLOGRAPHIC RECORDING IN BAYFOL HX PHOTOPOLYMER

Subject of Research. The paper presents experimental determination of the main shrinkage direction caused by photopolymerization during holographic recording in Bayfol HX material. Method. The determination method for the main shrinkage direction is based on registration of the change in volume holograms characteristics (period, the orientation of isophase planes relative to material surfaces and hologram thickness) caused by the shrinkage. For the implementation of this method a 2D-model is presented which describes shrinkage as a vector. The effect of the shrinkage on characteristics of holograms is evaluated based on geometrical laws. We performed modeling of the shrinkage with different directions and determined its effect on a variety of arbitrarily oriented holograms-gratings. Namely, the cases of isotropic shrinkage, as well as shrinkage in the direction of the material surfaces, the lattice vector and the isophase planes were considered. The experiment is carried out involving a simultaneous recording of two total internal reflection holograms in a photopolymerizable Bayfol HX composite. The changes of their characteristics make it possible to determine clearly the main shrinkage direction. Main Results. The main shrinkage direction has been determined along the less side of the material (considering thickness). However, the experiment has demonstrated a deviation of this direction along the lattice vector as well. Practical Relevance. The developed model and the experimental method allow for taking into account the shrinkage in Bayfol HX while modeling of photopolymerization and multicomponent diffusion in this material. The studied technique also facilitates predictions of hologram characteristics after the shrinkage aimed at its compensation.