Holographic gratings with different spatial frequencies recorded on BB-640 bleached silver halide emulsions using reversal bleaches

Abstract

The research made in the field of recording materials for holographic applications has yielded to materials of improving quality. Photographic emulsions have played an important role in this investigation, since although this is the first material used for recording purposes, there are a series of characteristics that convert the photographic emulsion in a very interesting material for holographic recording. In this work we will present the optimisation of a reversal bleaching process. This process has been largely used for Agfa 8E75 HD emulsions, but there is still a significant lack of information about it when used with BB-640 emulsions. There are some differences between BB-640 and Agfa 8E75 HD emulsions such as the degree of hardening of the gelatin, the mean grain size or the emulsion thickness. These differences must be taken into account in order to use the same chemical procedures commonly used for Agfa plates with BB-640 ones. For instance, one of these differences, the mean size of the silver halide grains present in the emulsion, influences directly in the scattering of the final hologram recorded in the emulsion. It will be demonstrated that the use of ultra-fine grained emulsions, such as BB-640, allows obtaining holograms with high diffraction efficiencies and low absorption and scattering. In particular, in this work a reversal bleach procedure will be optimised for diffraction gratings recorded with different spatial frequencies on BB-640 emulsions.