Direct measurement of the refractive index profile of phase gratings, recorded in silver halide holographic materials by phase-contrast microscopy

Plane-wave phase holograms recorded in Agfa-Gevaert 8E75HD emulsions and processed by the combination of AAC developer and the R-9 bleaching agent were studied by phase-contrast microscopy, using high-power immersion (100×) objective. Thus the modulation of the refractive index as a function of the bias exposure and the visibility of the recording interference pattern can also be determined. Measured diffraction efficiencies were compared to those predicted by coupled wave theory, using the measured refractive index modulations. Direct measurement of the phase profile of the gratings can be used for optimizing processing.