Fadeyeva T. Propagation and transformation of singular beams in anisotropic media

The manuscript is devoted to the study of propagation of different types of nonparaxial and paraxial singular beams along and at a small angle to the optical axis of an anisotropic uniaxial medium. The solution to the Maxwell equations has been found for nondiffracting beams propagating along the medium both with the linear and circular birefringence. The author has shown that axially symmetric birefringence of the medium induces formation of a centered degenerate polarization singularity (C-line) with the topological index +1 when transmitting a circularly polarized beam. Such a polarization singularity is associated with the optical vortex in the circularly polarized component with handedness opposite to that in the initial one, the vortex topological charge differing by two units from that in the initial beam. The effect is observed in the medium with the pure optical activity and also in the pure birefringent medium both for nonparaxial and paraxial beams. The author has revealed that the energy efficiency of the vortex generation can reach 100% for the highest order Hermit- and Laguerre-Gaussian beams of the complex argument. That high energy efficiency can be also reached for the monochromatic and polychromatic Bessel beams of the lowest order. The beam inclination with respect to the crystal optical axis results in recovering of the singular structure in the circularly polarized component with the opposite handedness. The beam recovery is accompanied with a lateral shift of the beam's center of gravity. This effect is the manifestation of the conservation law for the zz-component of the angular momentum flux along the crystal optical axis.