Comparative study of bleaches applied to BB-640 plates

The use of bleaching techniques is perhaps one of the most popular methods of creating phase holograms from holographic emulsions. In this paper we will study the influence of the different experimental conditions on the refractive index modulation created inside the hologram when bleaching techniques are used. A comparison will be made between three different kinds of bleach: a reversal bleach, a conventional bleach and a fixation-free rehalogenating bleach. It will be demonstrated that the necessary refractive index modulation can be achieved with conventional and fixation-free rehalogenating bleaches. The values of the diffraction efficiency are only limited by the absorption and scattering, which is very high in the case of conventional bleaches. It will also be found that the lowest values of absorption and scattering are obtained when the reversal bleach is used to obtain the volume holograms. In this case, the refractive index modulation stored in the hologram is not high and so the final diffraction efficiency is limited.This work was partially supported by “Ministerio de Ciencia y Tecnología”, Spain, under project MAT2000-1361-C04-04 and by “Generalitat Valenciana”, Spain, project GV01-130. Shirley Condeza and Ana María Campos wish to acknowledge a scholarship granted by the ‘Agencia Española de Cooperación Internacional (AECI)’