Planar volume phase holograms formed in bleached photographic emulsions

Abstract

Volume phase holograms are formed by a standard process in commercially available photographic emulsion. The material is characterized before recording, and initial experimental results are presented for reconstruction under index-matched conditions. An initial comparison is made using two-wave coupled-wave theory and a technique of curve fitting with experimental measurements of transmission and diffraction efficiency. The model works well close to the Bragg condition, but several differences are noted between theory and experiment away from the Bragg condition. An anomalous absorptive effect is noted in transmission. An improved model is then formulated, again using coupled-wave theory, and capable of analytic solution, taking into account phase and absorption modulation, a second harmonic in the grating profile and the appearance of some higher diffraction orders. Using this model, all the initial experimental results are satisfactorily explained, and the effect of spurious gratings in the hologram response is noted. The model is then used with an extensive set of experimental results to deduce the major characteristics of the material, including saturation of the modulation with exposure. The formulation of a mixed grating and possible dispersion of the modulation are also investigated. Suggestions are made for the design of more complicated components using this material and for material improvement.