Hybrid electromagnetic toroidal vortices

Abstract

The ubiquitous occurrence of toroidal vortices, or vortex rings, in fluid dynamics scenarios in nature has garnered notable attention in the scientific community, while their electromagnetic counterparts have only been proposed recently with two distinct manifestations: vector toroidal pulses and scalar phase toroidal vortices. Herein, we theoretically propose a form of electromagnetic toroidal vortex solutions that uniquely integrates both scalar and vector characteristics, challenging the prevailing notion of their mutual exclusivity. We also present an experimental generation of hybrid toroidal vortex pulses by a compact coaxial horn emitter augmented with a radial metasurface. These topological pulses exhibit peculiar electromagnetic features, such as vortex streets, skyrmions, and transverse orbital angular momentum, and may present advantages when propagating through perturbations, opening avenues for enhanced free-space information transmission, topologically nontrivial light-matter interaction, and microscopy techniques.