Effective ray equations for vortex light and their application in an optical waveguide

TL;DR

This paper derives effective ray equations for vortex light with orbital angular momentum, revealing an orbital Hall effect in optical waveguides, and models light-media interaction as light's free fall in curved spacetime.

Contribution

It introduces a novel derivation of ray equations for vortex light considering IOAM and models their propagation as free fall in curved spacetime.

Findings

Ray trajectory exhibits divergence similar to spin Hall effect

Orbital Hall effect caused by IOAM influences light propagation

Modeling as free fall in curved spacetime offers new insights

Abstract

Beyond its spin, light can also carry intrinsic orbital angular momentum (IOAM), termed as vortex light. In this study, we derive effective ray equations for vortex light by applying the WKB approximation to the covariant Maxwell equations. According to these equations, the propagation of vortex light can be significantly affected by its IOAM, as suggested by numerous studies. To examine the effects of IOAM, we solve the effective ray equations for vortex light and investigate its ray trajectory within a specific optical waveguide. Our findings indicate that the ray trajectory of vortex light exhibits a divergence perpendicular to the normal propagation plane, akin to the spin Hall effect in light. This divergence, termed as the orbital Hall effect, stems from the IOAM of the light. In this study, the effective ray equations are derived by modeling the interaction between light and media as light's free fall in a curved spacetime. Therefore, observing the orbital Hall effect could not only enhance our understanding of light's spin and IOAM, but also offer novel insights into the coupling between light and gravitational fields.