Influence of Refractive Indices Dispersion on Parameters of Imaging AOTFs Operating with Non-Polarized Light

The paper presents results on investigation of paratellurite based imaging tunable acousto-optic filters operating with arbitrary polarized light. We analyzed influence of dispersion of refractive indices in the crystal on a simultaneous satisfaction of the Bragg matching condition for ordinary and extraordinary polarized optical beams. The analysis was carried out at different optical wavelengths over the wide tuning range of the filters 400-1150 nm. Theoretical and experimental analysis of the problem proves that in a paratellurite tunable acousto-optic filter, the Bragg matching angle common for the two optical polarizations is varying in the limits up to 0.3°. This variation of the incidence angle may be as wide as a quarter of the filter angular aperture thus proving that the examined phenomenon should be considered in design of the imaging tunable acousto-optic filters