Optical polarization skyrmionic fields in free space

TL;DR

This paper demonstrates the creation of robust optical skyrmionic polarization fields in free space using spin-orbit coupling in nonparaxial optics and standing waves, revealing topologically protected structures without nonlinear interactions.

Contribution

It introduces a method to generate stable skyrmionic polarization structures in free-space optical beams through spin-orbit coupling and standing-wave configurations, expanding topological photonics.

Findings

Skyrmionic polarization fields are constructed in free space.

Structures exhibit topological protection without nonlinear effects.

Both Bloch and Néel textures are realized in the beams.

Abstract

We construct optical beams in free space with robust skyrmionic structures in their polarization fields, both in the electric spin vector for near-circular fields and in the polarization direction for near-linear fields, and for both Bloch (spiral) and N\'eel (hedgehog) textures. These structures are made possible by the spin-orbit coupling of tightly-focused nonparaxial optics as applied to higher-order Full-Poincar\'e beams, as well as by standing-wave configurations comprising forwards- and backwards-propagating waves. Our constructions show near-uniform circular and linear polarizations, providing a high degree of topological protection in the absence of nonlinear interactions.