Hybrid electromagnetic toroidal vortices

The ubiquitous occurrence of toroidal vortices or vortex rings in fluid-dynamic scenarios in nature has garnered significant attention of scientific frontier, whilst, the electromagnetic counterparts of which were only proposed recently with two distinct manifestations: vector toroidal pulses and scalar phase toroidal vortices. Herein, we theoretically propose a novel form of electromagnetic toroidal vortex solutions, that uniquely integrate both scalar and vector characteristics, challenging the prevailing notion of their mutual exclusivity. We also present the experimental generation of the hybrid toroidal vortex pulses by a compact coaxial horn emitter augmented with a radial metasurface, and we experimentally observe the formation of an electromagnetic vortex street within these pulses. These pulses reveal the connection between transverse orbital angular momentum, topological skyrmion textures, and spatiotemporal field. These attributes introduce new dimensions in topologically complex structured waves, opening avenues for enhanced free-space information transmission, topologically nontrivial light-matter interaction and microscopy techniques.

Methods
Theoretical, simulated, and measured results: calculated by matlab code, simulated by CST software, measured in anechoic chamber.