Rotational spin Hall effect in a uniaxial crystal

We have considered the propagation process of the phase-matched array of singular beams through a uniaxial crystal. We have revealed that local beams in the array are rotated when propagating. However the right and left rotations are unequal. There are at least two processes responsible for the array rotation: the interference of local beams and the spatial depolarization. The interference takes place in the vortex birth and annihilation events forming the symmetrical part of the rotation. The depolarization process contributes to the asymmetry of the rotation that is called the rotational spin Hall effect. It can be brought to light due to the difference between the envelopes of the dependences of the angular displacement on the inclination angle of the local beams or the crystal length reaching the value some angular degree. The direction of the additional array rotation is exclusively defined by the handedness of the circular polarization in the initial beam array.Comment: 26 pages, 11 figure

Nondiffracting vortex-beams in a birefringent chiral crystal

A vector wave analysis of nondiffracting beams propagating along a birefringent chiral crystal for the case of tensor character both of the optical activity and linear birefringence is presented, fields of eigen modes satisfying vector wave equation. We have written characteristic equations and found propagation constants and amplitude parameters of eigen modes. We have shown that the field of eigen modes is non-uniformly polarized in the beam cross-section. We have revealed that even a purely chiral crystal without a linear birefringent can generate optical vortices in an initially vortex-free Bessel beam.Comment: 9 pages, 5 figure

Natural shaping of the cylindrically polarized beams

We have experimentally and theoretically shown that the circularly polarized beam bearing singly charged optical vortex propagating through a uniaxial crystal can be split after focusing into the radially and azimuthally polarized beams in vicinity of the focal area provided that the polarization handedness and the vortex topological charge have opposite signs. Quality of the polarization structure can reach unity.Comment: 4 pages, 5 figure

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

We report the results of studies of torsion effect on the optical birefringence in LiNbO3 crystals. We have found that twisting of those crystals causes a birefringence distribution revealing non-trivial peculiarities. In particular, it has a special point at the center of cross section perpendicular to the torsion axis where zero birefringence value occurs. It has also been ascertained that the surface of the spatial birefringence distribution has a conical shape, with the cone axis coinciding with the torsion axis. We have revealed that an optical vortex, with the topological charge equal to unity, appears under the torsion of LiNbO3 crystals. It has been shown that, contrary to the q-plate, both the efficiency of spin-orbital coupling and the orbital momentum of the emergent light can be operated by the torque moment.Comment: 28 pages, 8 figure

Materials processing with tightly focused femtosecond vortex laser beams

This letter is the first demonstration of material modification using tightly focused femtosecond laser vortex beams. Double-charge femtosecond vortices were synthesized with the polarization-singularity beam converter described in Ref [1] and then focused using moderate and high numerical aperture optics (viz., NA = 0.45 and 0.9) to ablate fused silica and soda-lime glasses. By controlling the pulse energy we consistently machine high-quality micron-size ring-shaped structures with less than 100 nm uniform groove thickness.Comment: 8 pages, 3 figures, 10 references; submitted to Appl. Phys. Lett. on May 31, 201