Optimization of dichromated gelatin film coatings for holographic recordings

Abstract

Optimization of dichromated gelatin (DCG) film coatings for holographic recording is presented. The Taguchi optimization method is applied to DCG film coatings to obtain high uniformity. Two-level factorial design is used to optimize the emulsion curing conditions for high diffraction efficiency. Film thicknesses ranging from 6.0 to 23.4 mum are obtained with uniformities between 4.0 and 8.0%. Peak diffraction efficiencies between 87.0 and 96.9% are obtained using the optimized curing conditions. A possible holographic formation mechanism is introduced and experimental results for shrinkage and swelling are summarized. Both reflection type substrate mode holograms and polarization selective transmission type holograms are fabricated using optimized films. An improved Brewster angle method is also used to obtain an accurate measurement of the refractive index of DCG films, which are important in the design of holographic optical elements.