Supertoroidal light pulses: Propagating electromagnetic skyrmions in free space

TL;DR

This paper introduces a new family of complex, topologically nontrivial electromagnetic pulses with skyrmionic structures, expanding the understanding of toroidal light fields and their potential applications.

Contribution

It presents a generalized family of electromagnetic excitations with toroidal topology, including the Hellwarth-Nouchi pulse as the simplest case, characterized by a single parameter and diverse topological features.

Findings

Exhibits skyrmionic structures of various orders.

Displays multiple singularities in electromagnetic and Poynting vector fields.

Shows fractal-like energy backflow distributions.

Abstract

Topological structures of electromagnetic fields could give access to nontrivial light-matter interactions and additional degrees of freedom for information and energy transfer. A characteristic example of such electromagnetic excitations are space-time non-separable single-cycle pulses, the exact solutions of Maxwell equation of toroidal topology predicted by Hellwarth and Nouchi in 1996 and recently observed experimentally. Here we introduce a new family of electromagnetic excitation of toroidal topology with increasing complexity in which the Hellwarth-Nouchi pulse is just the simplest member. The electromagnetic excitations of the new family can be parametrised by a single real number and exhibit skyrmionic structures of various orders. They feature multiple singularities in the electromagnetic and Poynting vector fields are accompanied by the fractal-like distributions of energy backflow. The generalized family of toroidal electromagnetic excitation with salient topologies are of interest for transient light-matter interactions, ultrafast optics, spectroscopy, and toroidal electrodynamics.