Optical polarization singularities in metallic cavities excited by electric dipole sources

TL;DR

This paper explores the topological properties of optical polarization singularities inside metallic cavities excited by electric dipole sources, revealing new insights into their morphology, evolution, and topological transitions.

Contribution

It is the first to analyze the topological indices and mechanisms of PSs inside metallic cavities, including the emergence of polarization Mobius strips and transitions between different cavity geometries.

Findings

Identified the topological indices and morphologies of PSs inside spherical and torus cavities.

Discovered the mechanism behind polarization Mobius strips in spherical cavities.

Analyzed topological transitions connecting different cavity geometries.

Abstract

Optical polarization singularities (PSs) in real space carry rich topological properties and can enable highly precise manipulations of light fields. Conventional studies focus on the PSs in the open space of optical systems. The properties of PSs inside optical cavities remain largely unexplored. By using full-wave finite-element simulations, we investigate the optical PSs inside metallic cavities excited by electric dipole sources. We determine the topological indices, morphology, and spatial evolutions of the singularities inside both spherical and torus cavities. We uncover the relationship between spatial symmetries and the PSs, as well as the mechanism underlying the emergence of polarization Mobius strips in the spherical cavity. In addition, we investigate the topological transitions of the PSs connecting two geometries (i.e., sphere and torus) with distinct topologies. The results provide insight into the singular and topological properties of light fields in optical cavities and can find applications in optical sensing and optical manipulation of small particles.