Generation of optical vortex array in the course of acousto-optic diffraction

Generation of an array of optical vortices (OVs) with fractional charges under the conditions of acousto-optic Bragg diffraction is revealed experimentally. The OVs emerge in a wide diffracted optical beam due to reflection from a thick acousto-optic grating that contains bifurcated fringes of acoustic waves. Changes in the acoustic-wave frequency lead to deflection of the wide optical beam containing the OV array. The OVs preserve their spatial positions only in the narrow AW frequency range, while larger changes in the frequency imposes their movement out from the beam aperture, with appearance of the other OVs in the other places of the beam cross section.