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It has been shown that the acousto-optic Raman-Nath diffraction on the acoustic wave, which bears an acoustic vortex, is accompanied by the appearance of the diffraction maxima that bear an optical vortex. The charge of the vortices that appears as a result of the diffraction corresponds to the order of diffraction if the incident optical beam is the Gaussian beam and the charge of the acoustic vortex is equal to unity. When the incident optical vortex beam takes part in this process, the charge of the diffracted optical vortices is shifted on the charge value of the incident optical beam. As a result of the analysis, we obtained the relation for the charge of vortices of diffraction maxima. It has been found that the described effect can be used for controlled demultiplexing. [ABSTRACT FROM AUTHOR]

We show how a singularity of optical field can be used for determination of piezooptic coefficient of crystals under their torsion, in particular in the situation when the natural optical activity makes direct polarimetric experiments too complicated. Experimental studies of an optical vortex appearing under torsion of lead germanate crystals have enabled us to determine so-called non-principal coefficients (π1414 and π1425). A relationship between the spin angular momentum of light beam and the piezooptic coefficients has been derived. [ABSTRACT FROM AUTHOR]

In the present work we describe a high-accuracy torsion method for measuring piezooptic coefficients π14 and π25 in trigonal crystals. Spatial distributions of the optical indicatrix orientation and the optical birefringence induced by torsion stresses are quantitatively evaluated and analysed. It is shown that a crystal subjected to torsion stresses works as an optical lens, with the characteristics operated by a torque moment. [ABSTRACT FROM AUTHOR]

We demonstrate both theoretically and experimentally that a linearly polarized optical beam incident on a linearly dichroic nematic liquid crystal cell with a topological defect of the topological strength q and linear dichroism, transforms into a composite vector beam consisting of elementary vector beams with the polarization singularity orders m=2q and m=q. Consequently, it has been proved that due to the linear dichroism a liquid crystal defect of the topological strength q=1 transforms an incident circularly polarized beam into a composite vortex beam consisting of the double-charged vortex beam and vector-vortex beam with polarization order and topological charge that are equal to unity. [ABSTRACT FROM AUTHOR]

An optical conversion of spin angular momentum to orbital angular momentum (SAM-to-OAM) that appears in Bi12GeO20 crystals under the effect of conically shaped external electric field due to a Pockels effect has been studied both experimentally and theoretically. We have revealed the appearance of a doughnut mode and an optical vortex in the system consisting of a right-handed circular polariser, a sample subjected to conical electric field, and a left-handed circular analyser. It has been found that the presence of natural optical activity leads to notable decrease in the efficiency of the SAM-to-OAM conversion. [ABSTRACT FROM AUTHOR]

We have suggested a highly precise method for determining piezooptic coefficients, which relies on a knowledge of 2D spatial distribution of mechanical stresses in a crystalline disk compressed along its diameter. Relevant theoretical relations that describe piezooptic effect in the crystals belonging to the point symmetry group 3m have been derived. The method has been successfully verified in the experiment dealing with LiNbO3 crystals. [ABSTRACT FROM AUTHOR]

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 2 π 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 .

Generation of an array of optical vortices (OVs) with fractional charges under the condition 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 (AWs). Changes in the AW 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 impose their movement out from the beam aperture, with appearance of the other OVs in the other places of the beam cross section.

We have revealed that torsion stresses produce an optical activity effect in initially isotropic glass media. The optical activity caused by spatially inhomogeneous mechanical stresses has been experimentally studied for a standard glass BK7 subjected to torques, using a single-beam polarimetry and a polarizer-sample-analyzer scheme. The torsion-gyration coefficient for the BK7 glass has been determined as (3.96±0.82)×10 -17   m 3 /N.

We have revealed topological defects (TDs) of the angle of optical indicatrix (OI) orientation in a glass Li2B4O7 sample, which originate from the specific spatial distribution of optical birefringence caused by residual mechanical stresses. It has been found that the strength of TDs of the OI rotation angle is equal to ±1/2. Following from the experimental results, we have shown that the regions around the TDs of OI orientation are those of a 3D stressed state. We have formulated criteria for determining whether 2D or 3D distributions of the optical anisotropy parameters appear, based on the TDs of OI orientation. It has been shown that, in some particular cases, the regions with the TDs can testify the availability of a 2D stressed state. Besides, we have demonstrated experimentally that the TDs can appear for more than one projection in the case of 3D distributions of the OI parameters, which appear under bending of glass plates by a distributed load.