Triple Bragg Diffraction of Bessel Light Beams by Ultrasound in Uniaxial Crystals

Noncollinear triple acousto-optic diffraction of Bessel light beams by ultrasound in uniaxial crystals is investigated. An expression for the complex vector amplitude of a wave diffracted under exact Bragg synchronism conditions is obtained in vector-matrix form. The diffracted light beams display triple Bragg diffraction with different efficiencies when a Bessel light beam propagates at a small angle to the crystal optical axis. Diffraction where the diffracted light beams have the same intensity is possible if the Bragg synchronism conditions are exactly fulfilled. This diffraction feature is not observed without Bragg synchronism. The light intensity in the third diffraction order is significantly reduced (down to zero) with large frequency detuning of the Bragg synchronism.