Influence of optical activity of gyroanisotropic crystals on Bessel beams

It is shown that a Bessel beam with initial circular polarization, propagating through an optically active medium devoid of linear birefringence, generates an optical vortex on the axis in the orthogonally polarized component. The possibility of mutual transformation of beams with radial and azimuthal polarization distributions in a medium with pure optical activity is presented. It is proved that under a weak external perturbation of a medium with pure optical activity and linear birefringence, the isotropic point is destroyed. A description is given of how a medium with a combined type of anisotropy reacts as a medium with pure linear birefringence and is suppressed by linear birefringence in the vicinity of this isotropic point. The polarization structure of the fields of eigenmodes of Bessel beams in a birefringent uniaxial crystal with optical activity is similar to the structure of the modes of a medium with pure optical activity. The applicability of these studies may broaden the understanding of physical processes in the emerging field of polarization and phase profilometry of materials.