Effect of Emulsion Thickness on the Diffraction Efficiency of Amplitude Holograms

The diffraction efficiency of amplitude holograms recorded on photographic emulsions is shown to be independent of the thickness of the emulsion layer. This can be explained theoretically under the assumption that the exposure modulation is not too high, i.e., for high and moderate beam ratios K. With this assumption it is possible to demonstrate the equivalence of Kogelnik’s equation using a coupled-wave theory for thick holograms and the equations derived by Kaspar and Lamberts for thin holograms. This is true even though the former contains an explicit dependence on thickness and the latter equation includes only the MTF of the emulsion and the slope of the amplitude-transmittance log-exposure characteristic of the emulsion. This conclusion is demonstrated experimentally by measuring the diffraction efficiency for two series of very-fine-grain emulsions, which differ only in the thickness of the emulsion layer.