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We demonstrate the generation of acoustic vortex beams with the aid of an acoustic spiral phase plate and an acoustic grating having a fork-like bifurcation of its slits. The acoustic vortex beam generated in this manner influences the particles floating on a water surface and rotates them. Our experiments show that the intensity of the acoustic vortex beam increases from zero in its center to a certain maximal value near the shell of the beam. The phase of the beam changes by the angle 2π whenever the azimuthal angle is changed by the same value. We also study acousto-optic diffraction of the optical beam by the acoustic beam bearing a vortex and demonstrate that each of the appropriate diffraction maxima are split into two maxima. The latter correspond to diffraction by the elementary acoustic rays which are close to the opposite edges of the acoustic vortex beam. A dark region between the maxima appears due to destructive interference of the elementary optical rays originated from the diffraction by the opposite sides of the acoustic vortex beam, which are phase-shifted by π.

We determine full matrices of piezo-optic and elasto-optic coefficients for lead germanate crystals

In the present work, we analyze acousto-optic (AO) interactions under the condition when a diffracted optical wave propagates along one of the optic axes in optically biaxial crystals. We find that the number of AO interaction types is reduced from nine, which is typical for the most general case, to six, since some of the isotropic and anisotropic diffraction types manifest themselves simultaneously. We reveal that, in the case of the interactions of quasi-ordinary and quasi-extraordinary optical waves, the dependences of effective elasto-optic coefficients and AO figure of merit on the tracing angle of an incident optical beam around the optic axis are symmetric with respect to the plane that is perpendicular to the plane of optic axes and contains the principal axis

We analyze the effect of acoustic wave (AW) polarization states deviation from purely longitudinal and transverse on the anisotropy of the acousto-optic (AO) figure of merit for the case of AO interactions occurring in the principal crystallographic planes. In particular, we obtain phenomenological relations that describe the effective elasto-optic coefficient for the six types of AO interactions, which exhaust all of the possible isotropic AO diffractions. These relations are compared for the alternative cases when the deviations of polarization of the AWs from purely longitudinal and transverse ones are either taken into consideration or completely neglected. Our analysis carried out on the example of