Orbital angular momentum multiplication in plasmonic vortex cavities

TL;DR

This paper introduces a novel method to generate and control plasmonic orbital angular momentum using structural boundary reflections, demonstrated through experimental vortex cavities with increasing topological charge over time.

Contribution

It presents the first experimental realization of plasmonic vortex cavities that generate dynamically evolving orbital angular momentum via boundary reflections.

Findings

Generated vortex pulses with increasing topological charge over time

Tracked angular momentum growth within cavities for over 300 femtoseconds

Demonstrated control of plasmonic orbital angular momentum through structural boundaries

Abstract

Orbital angular momentum of light is a core feature in photonics. Its confinement to surfaces using plasmonics has unlocked many phenomena and potential applications. Here we introduce the reflection from structural boundaries as a new degree of freedom to generate and control plasmonic orbital angular momentum. We experimentally demonstrate plasmonic vortex cavities, generating a succession of vortex pulses with increasing topological charge as a function of time. We track the spatio-temporal dynamics of these angularly decelerating plasmon pulse train within the cavities for over 300 femtoseconds using time-resolved Photoemission Electron Microscopy, showing that the angular momentum grows by multiples of the chiral order of the cavity. The introduction of this degree of freedom to tame orbital angular momentum delivered by plasmonic vortices, could miniaturize pump-probe-like quantum initialization schemes, increase the torque exerted by plasmonic tweezers and potentially achieve vortex lattice cavities with dynamically evolving topology.