Optical vortices in antiguides

Abstract

We address the question of whether an optical vortex can be trapped in a dielectric structure with a core of a lower refractive index than the cladding--namely an antiguide. Extensive numerical simulations seem to indicate that this inverse trapping of a vortex is not possible, at least in straightforward implementations. Yet, the interaction of a vortex beam with a curved antiguide produces interesting effects, namely a small but finite displacement of the optical energy center-of-mass and the creation of a symmetrical vortex-antivortex pair on the exterior of the antiguide.

Nondiffracting chirped Bessel waves in optical antiguides

“…The result is quite remarkable: The wave is attracted toward the high-index region along a curved trajectory in the direction of the displacement (x in this example) while retaining its transverse profile. the difference of these results with the similar numerical experiment reported in [21] using a simple Laguerre-Gauss mode with vorticity m = 1. In the latter case and due to the absence of some special structure in its wavefront, the wave gets severely distorted.…”

“…In the absence of some special structure in its wavefront, such a wave has no chances to survive the defocusing action of the antiguide and thus spreads quickly. These results already suggest that chirped Bessel waves can outperform standard waves (like Gaussian or the simple Laguerre-Gaussian modes used in [21]) in applications where light has to be guided in a diffraction-resisting manner in unstable optical potentials. Let us now test our waves under some abnormal conditions.…”

“…Closing this introduction, we would like to mention that the question of trapping vortex waves in an optical antiguide was addressed recently. [21] In this work simple vortex modes of the Laguerre-Gauss type were launched in curved antiguides with a Gaussian index profile hoping to observe some trapping effect and guidance of the vortex along the antiguide. The conclusion was negative as the test waves had no special structure (for example chirp) in the radial direction.…”

Vortex confinement and bending with nonlocal solitons

“…The bending of vortex beams, conversely, has never been successfully dealt with to date. A previous case study of vortices and antiguides revealed that antiguides are unable to confine vortices or prevent their breakup [17]. In this Letter, using modulation theory and numerical experiments, we address the possibility of guiding and routing signals in the shape of vortex beams along curved trajectories, exploiting the transverse confinement afforded by nonlocal solitons.…”

Soliton Aided Propagation and Routing of Vortex Beams in Nonlocal Media

“…In the present work, with specific reference to nematic liquid crystals, but without loss of generality, we address the stabilization and guidance of vortex beams by means of nonlocal bright spatial solitons, using modulation theory for and numerical solutions of the equations governing the nonlinear, nonlocal response of reorientational media. At variance with ``sombrero'' refractive potentials, such as in antiguides [18], a bright soliton induces a dielectric waveguide and can, in some cases, confine and route a complex wavepacket such as a vortex. In this Paper we investigate collinear soliton-vortex pairs interacting with a dielectric interface and undergoing angular deviation by either refraction or total internal reflection.…”