Transverse Shifts and Time Delays of Spatiotemporal Vortex Pulses Reflected and Refracted at a Planar Interface

TL;DR

This paper investigates how spatiotemporal vortex pulses with transverse orbital angular momentum experience novel transverse and longitudinal shifts upon reflection and refraction, enabling OAM-controlled pulse delays and propagation speeds without dispersion.

Contribution

It introduces new theoretical and numerical findings on OAM-dependent shifts and time delays of spatiotemporal vortex pulses at planar interfaces, revealing novel effects not previously known.

Findings

Discovery of OAM-dependent transverse and longitudinal shifts.

Identification of time delays as a form of pulse propagation control.

Potential for OAM-based manipulation of pulse speed without dispersion.

Abstract

Transverse (Hall-effect) and Goos--H\"{a}nchen shifts of light beams reflected/refracted at planar interfaces are important wave phenomena, which can be significantly modified and enhanced by the presence of intrinsic orbital angular momentum (OAM) in the beam. Recently, optical spatiotemporal vortex pulses (STVPs) carrying a purely transverse intrinsic OAM were predicted theoretically and generated experimentally. Here we consider the reflection and refraction of such pulses at a planar isotropic interface. We find theoretically and confirm numerically novel types of the OAM-dependent transverse and longitudinal pulse shifts. Remarkably, the longitudinal shifts can be regarded as time delays, which appear, in contrast to the well-known Wigner time delay, without temporal dispersion of the reflection/refraction coefficients. Such time delays allow one to realize OAM-controlled slow (subluminal) and fast (superluminal) pulse propagation without medium dispersion. These results can have important implications in various problems involving scattering of localized vortex states carrying transverse OAM.