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Diffraction Efficiency of Hologram Gratings with Modulation Changing through the Thickness

The behavior of a thick hologram is examined for gratings recorded holographically on Kodak 649F photographic plates by using a He-Ne laser. Interference fringes in the grating emulsions are observed with an optical microscope, and it is shown that the contrast of the fringes decreases from the emulsion surface to the base. The observed result is taken into consideration in applying the coupled wave theory, and numerical evaluations of a simple analytical expression are compared with measurements of the dependence of the diffraction efficiency on the angle of incidence for the amplitude and phase hologram gratings, and the amount of the decrease in the grating modulation is found.