Diffraction efficiency of transmission holograms

The coupled wave theory predicts oscillations of the diffraction efficiency for thick holographic transmission phase gratings with increasing Bragg angle. In order to examine this relationship the theory published by Kogelnik was recalculated using more accurate boundary conditions and applying an eigenvalue procedure. The results are in agreement with the equations already published. Experiments were performed to measure the diffraction efficiency as a function of the Bragg angle (theta) and refractive index variation. The few experiments indicate no oscillations for high values of (theta) . Diffraction efficiency shows the same dependency on refractive index variation for low and high values of Bragg angle. The findings are not in full agreement with theory. Absorption cannot account for all deviations. The experimental results help to find ideal conditions producing transmission holograms.