Bleached holograms are one of the most interesting techniques used to produce phase holograms of high quality on photographic emulsions. Of particular interest is the method of fixation-free rehalogenating bleaching. Using Kogelnik's coupled-wave theory we shall obtain information about the characteristics of the final holograms recorded in bleaching procedures. In this way, it is possible to analyse the particular mechanisms involved in the formation of the holograms. In this paper we study the influence of the different experimental conditions on the refractive index modulation created inside the hologram. It will be demonstrated that it is possible to maintain the values of diffraction efficiency over a wide range of exposures if the correct experimental conditions are chosen. On the other hand, it will also be demonstrated that the use of fixation-free rehalogenating bleaching techniques allows high-refractive-index modulations to be obtained. Moreover, it is possible to attain a theoretical diffraction efficiency of 100%, which is only limited by absorption and scattering.
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