Bulk-to-surface coupling of spatiotemporal vortices

TL;DR

This paper investigates how to efficiently couple bulk spatiotemporal vortex pulses to surface waves like surface plasmon-polaritons, addressing the challenges posed by their different dispersion relations through specific mechanisms and numerical simulations.

Contribution

It introduces three mechanisms for bulk-to-surface conversion of spatiotemporal vortex pulses, advancing understanding of wave coupling at interfaces.

Findings

Identified three mechanisms enabling STVP-to-SPP coupling.

Numerical simulations demonstrate effective conversion at dielectric-metal interfaces.

Provided insights into overcoming dispersion mismatch challenges.

Abstract

We consider the coupling of bulk space-time-structured waves, such as spatiotemporal vortex pulses (STVPs), to surface waves, such as surface plasmon-polaritons (SPPs). For resonant coupling that preserves the frequency and tangent wavevector components, it is challenging to transfer the space-time wave structure because of the difference between the bulk and surface wave dispersions. We describe three mechanisms allowing for the bulk-to-surface conversion of STVPs: (i) a suitable tilt of the pulse spectrum in the $(\omega,{\bf k})$ space; (ii) confinement of the incident pulse in the direction orthogonal to the vortex; and (iii) losses in the surface waves. We supply general considerations with numerical simulations of the STVP-to-SPP coupling at a dielectric-prism/metal-film interface.