Propagation dynamics of auto-focusing Bessel Gaussian beam in a chiral medium

Abstract

In this paper, propagation characteristics of auto-focusing Bessel Gaussian beam (ABGB) and auto-focusing Bessel Gaussian vortex beam (ABGVB) with double foci in the chiral medium are studied for the first time. Effects of beam parameters, such as the beam waist width, the initial beam focal length, the topological charge of optical vortex, and the chiral medium parameter on the auto-focusing behavior of ABGB and ABGVB are investigated. The results indicate that by adjusting the beam waist width of ABGB could manipulate the focal length depth and the auto-focusing ability of left-circularly polarized (LCP) and right-circularly polarized (RCP) components in the chiral media. The focal lengths, the focal length depths, and the auto-focusing abilities of LCP and RCP components can be controlled by the initial beam focal length of ABGB. The focal length and the focal length depth of RCP can be modulated by the chiral medium parameter effectively. Optical vortex results in a dark hollow channel in the optical field of ABGVB propagating in the chiral media, and the topological charge determines the width of dark hollow. The optical vortex and the beam waist width do not affect the focal length of LCP and RCP, while the initial beam focal length of ABGVB and the chiral medium parameter could be adopted to manipulate the focal lengths of ABGVB, especially the manipulation of RCP focal length.