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

Fine structure of perturbed Laguerre-Gaussian beams: Hermite-Gaussian mode spectra and topological charge

We found that small perturbations of the optical vortex core in the Laguerre-Gaussian (LG) beams generate a fine structure of the Hermite-Gauss (HG) mode spectrum. Such perturbations can be easily simulated by weak variations of amplitudes and phases of the HG modes in the expansion of the LG beam field. We also theoretically substantiated and experimentally implemented a method for measuring the topological charge of LG beams with an arbitrary number of ring dislocations. Theoretical discussion and experimental studies were accompanied by simple examples of estimating the orbital angular momentum and the topological charge of perturbed LG beams.Comment: 16 pages, 7 figure