Collinear aconsto-optic interaction of diveirgent beams in paratellurite crystal

Theoretical and experimental investigation of collinear diffraction of divergent optic beams by ultrasonic waves near by the direction [110] of paratellurite crystal has been carried out. The diffraction has been examined in direction [110] forbidden in TeO2 for acousto-optic interaction in the case of plane waves. It has been shown that the collinear diffraction along this direction exists only for divergent light and sound waves while efficiency of the diffraction increases with the growth of the divergence. The effect has been examined at the acoustic frequency f approximate to 149 MHz and the wavelength of the non-collimated light lambda = 633 nm with the optical spreading up to 4 degrees. A collinear acousto-optic filter on paratellurite applying the diffraction has the length of interaction l = 2.7 cm. It has been proved that acoustic attenuation causes a decrease of efficiency of the diffraction and a broadening of a bandwidth of the device. The spectral resolution value as high as R similar to 3000 has been obtained lambda = 633 nm. The diffraction efficiency I-1 / I-0 approximate to 0.8 and the wide-angle aperture Delta phi approximate to 4 degrees give perspectives to use the collinear diffraction in filters on the base of TeO2 crystals.