Evaluation of a technique for the design and manufacture of an off-axis holographic lens in dichromated gelatin

Variations in the intensities of the recording waves during the exposure of a holographic film cause fluctuations in the average intensity and the modulation depth of the resulting fringe pattern. The development process of the holographic layer stores these fluctuations and converts them into a variation of the diffraction efficiency and of the layer thickness if the exposure is in the linear range of the layer. In this paper a processing technique for dichromated gelatin layers is developed which results in a homogeneous distribution of the diffraction efficiency over the hologram aperture and restores the original layer thickness. Using this processing technique, two different types of off-axis holographic lens have been developed. The resulting local Bragg angles, the diffraction efficiencies and the layer thickness were determined by fitting the angular sensitivity curves of the lenses using Kogelnik's coupled wave theory.