Acousto-optic interaction between circularly polarized optical eigenwaves: example of AgGaS crystals.

We analyze acousto-optic (AO) diffraction occurring at the light wavelength of a so-called "isotropic point" in AgGaS crystals. It is shown that a natural optical activity, which manifests itself as circular birefringence at the isotropic point, can lead to two different types of AO Bragg diffraction, isotropic and anisotropic. The first type concerns the interaction of circularly polarized optical eigenwaves with the same sign of rotations of their electric-field vectors.

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

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.

Torsion-induced optical rotation in isotropic glass media.

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.

Crossover regime of optical vortices generation via electro-optic nonlinearity: the problem of optical vortices with the fractional charge generated by crystals.

In this work, we analyze the behavior of topological defects of optical indicatrix orientation induced by a conically shaped electric field in crystals in a crossover regime that appears at intermediate fields separating the regimes of prevailing Pockels and Kerr electro-optic nonlinearities. We have found that increases in the electric voltage applied to a crystal induce neither topological defects, with the strengths being not multiples of ½, or the optical vortices with fractional charges. Instead, there appear some additional topological defects of the optical indicatrix orientation, the behavior of which we have studied in detail.

Topological defects of optical indicatrix orientation in stressed glasses: spatial distribution of optical anisotropy parameters.

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.

Generation of double-charged optical vortices on the basis of electro-optic Kerr effect.

We show that double-charged optical vortices can be generated with the help of Kerr electro-optic effect in either single crystals or isotropic media, including gaseous and liquid ones. We analyze possibilities for the vortex generation via the Kerr effect for different point groups of symmetry and formulate the appropriate conditions. We prove that the crystals, textures, and the isotropic media most suitable for the generation of double-charged optical vortices should belong to the symmetry groups 622, 6mm, 6/mmm, 6, 6/m, ∞/m, ∞, ∞2, ∞mm, ∞/mmm, ∞/∞/mmm, and ∞/∞2.

Induction of optical vortex in the crystals subjected to bending stresses.

We describe a method for generation of optical vortices that relies on bending of transparent parallelepiped-shaped samples fabricated from either glass or crystalline solid materials. It is shown that the induced singularity of optical indicatrix rotation leads in general to appearance of a mixed screw-edge dislocation of the phase front of outgoing optical beam. At the same time, some specified geometrical parameters of the sample can ensure generation of a purely screw dislocation of the phase front and, as a result, a singly charged canonical optical vortex.

Generation of doubly charged vortex beam by concentrated loading of glass disks along their diameter.

We show that a system of glass disks compressed along their diameters enables one to induce a doubly charged vortex beam in the emergent light when the incident light is circularly polarized. Using such a disk system, one can control the efficiency of conversion of the spin angular momentum to the orbital angular momentum by a loading force. The consideration presented here can be extended for the case of crystalline materials with high optical damage thresholds in order to induce high-power vortex beams.

Spin-to-orbit conversion at acousto-optic diffraction of light: conservation of optical angular momentum.

Acousto-optic diffraction of light in optically active cubic crystals is analyzed from the viewpoint of conservation of optical angular momentum. It is shown that the availability of angular momentum in the diffracted optical beam can be necessarily inferred from the requirements of angular momentum conservation law. As follows from our analysis, a circularly polarized diffracted wave should bear an orbital angular momentum.

Appearance of singularities of optical fields under torsion of crystals containing threefold symmetry axes.

We present an analysis of the effect of torsion stresses on the spatial distribution of optical birefringence in crystals of different point symmetry groups. The symmetry requirements needed so that the optical beam carries dislocations of the phase front are evaluated for the case when the crystals are twisted and the beam closely corresponds to a plane wave. It is shown that the torsion stresses can produce screw-edge, pure screw, or pure edge dislocations of the phase front in the crystals belonging to cubic and trigonal systems.

On determination of sign of the piezo-optic coefficients using torsion method.

We have shown that a high-accuracy torsion method recently developed by the authors for measuring piezo-optic coefficients allows determining not only the absolute value of the coefficients but also their sign. The techniques and experimental procedures used for determination of the sign are described in detail and proven based on studies of α-BaB2O4 and LiNbO3 crystals. The piezo-optic coefficients are determined for both crystals, and a combination of the corresponding photoelastic coefficients is determined for the case of α-BaB2O4 crystals.

Optical anisotropy induced by torsion stresses in LiNbO3 crystals: appearance of an optical vortex.

We report the results of studies of the torsion effect on the optical birefringence in LiNbO(3) crystals. We found that the twisting of those crystals causes a birefringence distribution revealing nontrivial peculiarities. In particular, they have a special point at the center of the cross section perpendicular to the torsion axis where the zero birefringence value occurs.