Dichromated gelatin has been established as the most frequently used recording material for the production of holographic optical elements. New applications are being found for photopolymers in previously unexplored areas such as holographic interconnect systems.
However, photographic emulsion from the beginning has been and continues to be the most used holographic recording material. This is due to its relatively high sensitivity and ease of processing, the availability of improved processing chemistries and commercial films, and the repeatibility of the results. We analyze different sources of noise in photographic emulsions (such as intermodulation noise, noise gratings, and nonlinear noise) and the influence of the photochemical process on those noise sources. Bleached emulsions using rehalogenating and solvent processes are considered, and silver-halide-sensitized gelatin is discussed as a medium for transmission holograms. New developers and new noise models are presented on the supposition that the nonlinear response of the recording material is due to the photochemical process.