Free-Space Propagation and Skyrmion Topology of Toroidal Electromagnetic Pulses

TL;DR

This paper experimentally investigates the propagation dynamics and topological structures of microwave toroidal electromagnetic pulses, revealing their evolution towards increased space-time nonseparability and specific topological configurations.

Contribution

It provides the first experimental mapping of skyrmionic textures in microwave toroidal pulses and analyzes their evolution during propagation.

Findings

Microwave toroidal pulses can be generated using a broadband conical horn antenna.

The topological textures of the pulses evolve towards stronger nonseparability during propagation.

The pulses approach the canonical Hellwarth and Nouchi toroidal pulse configurations.

Abstract

Toroidal electromagnetic pulses have been recently reported as nontransverse, space-time nonseparable topological excitations of free space [Nat. Photon. 16, 523-528 (2022)]. However, their propagation dynamics and topological configurations have not been comprehensively experimentally characterized. Here, we report that microwave toroidal pulses can be launched by a broadband conical horn antenna. We experimentally map their skyrmionic textures and demonstrate how that during propagation the pulses evolves towards stronger space-time nonseparability and closer proximity to the canonical Hellwarth and Nouchi toroidal pulses.