Photoelastic and Acousto-optic Properties of KDP Crystal Applied in Wide Angle Tunable Filters

AbstractThe paper presents results on calculation and measurement of acousto-optic properties of KDP crystals applied in imaging tunable acousto-optic filters operating in the ultraviolet region of electromagnetic light. Effective photoelastic coefficients and acousto-optic figures of merit are evaluated in the mode of wide angle diffraction. The carried out analysis is based on results of measurements of the efficiency of Bragg diffraction at the same frequency of ultrasound but at two different angles of light incidence in the KDP crystal. We used the crystal in an imaging acousto-optic tunable filter operating at the wavelengths of light 405, 532 and 633nm. The filters apply a slow shear acoustic wave propagating at the angles α=90 and α=120 relatively to the [100] axis in (010) plane of the crystal. Differences between the measured data on the photoelastic coefficients and those found in literature are discussed in the presentation