Reversed propagation dynamics of Laguerre-Gaussian beams in left-handed materials

TL;DR

This paper investigates how Laguerre-Gaussian beams behave in left-handed materials, revealing reversed wave-front rotation, Poynting vector spiral, and momentum properties due to negative phase velocity and Gouy-phase shift.

Contribution

It provides a theoretical analysis of the reversed propagation dynamics of Laguerre-Gaussian beams in left-handed materials based on angular spectrum representation.

Findings

Reversed wave-front screw due to negative phase velocity

Inverse spiral of Poynting vector caused by negative Gouy-phase shift

Angular momentum remains unchanged despite reversed linear momentum

Abstract

On the basis of angular spectrum representation, the reversed propagation dynamics of Laguerre-Gaussian beam in left-handed materials (LHMs) is presented. We show that negative phase velocity gives rise to a reversed screw of wave-front, and ultimately leads to a reversed rotation of optical vortex. Furthermore, negative Gouy-phase shift causes an inverse spiral of Poynting vector. It is found that the Laguerre-Gaussian beam in LHMs will present the same propagation characteristics as the counterpart with opposite topological charges in regular right-handed materials (RHMs). The momentum conservation theorem insures that the tangential component of the wave momentum at the RHM-LHM boundary is conserved. It is shown that although the linear momentum reverses its direction, the angular momentum remains unchanged.