Asymmetric channel isolation in multichannel acousto-optic cells made of tellurium dioxide crystal

Abstract

Direction [110] in the TeO 2 crystal has unique acoustic and acousto-optic properties. This direction is widely used in many applications. But a slow shear acoustic wave travelling in this direction looks very unpromising for multichannel acousto-optic cells because of its low channel-to-channel isolation under reasonable channel package density.This low isolation is due to the abnormally high physical spread of this slow shear wave travelling in the [110] direction, and the therefore high value of the acoustic anisotropy coefficient b = 26. During recent investigations, a direction exhibiting self-collimation with the coefficient b ≈ 0.3 was found. This direction lies in the optical plane under the angle of 29 o with respect to the [110] axis. But the acousto-optic figure of merit M 2 appears smaller for this direction.A number of directions in the TeO 2 crystal's optical plane combining acceptable values of the acousto-optic figure of merit M 2 and channel-to-channel insulation under high channel package density have been experimentally and theoretically studied. Discussed and analyzed are the features of these directions when they are used in multichannel acousto-optic cells with the wideband anisotropic diffraction.