New mechanism for polarization singularity of vector vortex beams

TL;DR

This paper investigates the origin of polarization singularities in vector vortex beams, linking them to the Stratton vector and the polarization bases determined by Maxwell's equations, and discusses their polarization structure.

Contribution

It reveals that the polarization singularity arises from the polarization bases associated with the Stratton vector in the integral representation of vector vortex beams.

Findings

Polarization singularities are linked to the Stratton vector.

The polarization bases become singular when parallel to the Stratton vector.

The polarization structure's consistency with the bases is analyzed.

Abstract

It was recently realized that the polarization bases of the plane-wave modes in the integral representation of a light beam need to be determined by a degree of freedom arising from the divergence-free Maxwell's equation. This is a frequently introduced real unit vector in the literature, called Stratton vector. The polarization bases so determined are singular at the momentum that is parallel to the Stratton vector. Here we show that the polarization singularity of vector vortex beams given by the integral representation comes from the singularity of the polarization bases in association with the Stratton vector. The consistency of the polarization structure of the vector vortex beams with their polarization bases is also discussed.