Non-canonical propagation of high-order elliptic vortex beams in a uniaxially anisotropic medium

Abstract

We have analysed propagation of nonparaxial and paraxial beams perpendicular to the optic axis in a uniaxially anisotropic medium (unbounded optically uniaxial crystal). We have presented the paraxial solutions in the form of generalised Hermite-Gaussian beams propagating perpendicular to the optic axis in a uniaxially anisotropic medium. We have also constructed the generalised Laguerre-Gaussian beams at the z=0 plane and analysed their evolution in a homogeneous isotropic medium. Comparing it with the evolution of standard Laguerre-Gaussian beams with n=0 and m≠0 in the crystal, we have revealed that the additional elliptic deformation of the extraordinary beam results in topological reactions that essentially distort the field structure for the account of different rotation rates of the vortex row originated from the centred degenerate optical vortex and the conoscopic pattern. We have predicted conversion of the vortex topological charge at the beam axis similar to that in astigmatic lenses and analysed the radical differences with this process. We have revealed synchronic oscillations of the spin angular momentum and the sign of the vortex topological charge at the beam axis.

Optical vortex conversion in the elliptic vortex-beam propagating orthogonally to the crystal optical axis: the experiment

“…In the present paper we focus our attention on the experimentally studied structural transformations of the elliptical vortex beams propagating perpendicular to the crystal optical axis. In the theoretical aspect it was found that solutions for the paraxial wave equation can be expressed in the form of the generalized Laguerre-Gaussian beams bearing high-order optical vortices [8]. Article contains two sections: the second chapter is devoted to theoretical explanation of sign-conversation phenomenon in uniaxial crystal; in the third section the results of experimental observation are displayed.…”

Generation of optical vortices in rotating uniaxial crystal for light propagation along the perpendicular to its optical axis

“…It is known that conversion of the elliptical singular beams has periodical features taking place along the beam axis z propagating along the perpendicular to the crystal optical axis [2]. The most interesting case springs up when the beam propagates nearly perpendicular to the optical axis with the deviation angle 7º so that 0 0 sin    .…”

“…In case the beam bears the optical vortex then the crystal changes the singular structure of the vortex. The slight changes of the crystal parameters can result in the critical transformations of the phase singularity [2][3][4]. However the question of the vortex generation in this case remains open.…”

A Novel Perspective of a Laguerre–Gaussian Beam's Phase Acceleration in Chiral Medium by Using Distinguishability Property

“…2(a)). The effective beam can be approximately modelled with an elliptical Gaussian beam envelope covering a non-canonical vortex [30] (i.e. is not singular, but has a geometry and evolves continuously in z ).…”