Dynamics of Transverse Spin and Longitudinal Fields of Cylindrical Vector Beams in Optically Active Media

TL;DR

This paper analyzes how cylindrical vector beams' polarization evolves in optically active media, revealing periodic mode conversions, spin rotation, and pulsing fields with implications for advanced optical applications.

Contribution

It introduces a theoretical and experimental framework for understanding polarization dynamics of cylindrical vector beams in chiral media, highlighting novel mode conversion phenomena.

Findings

Periodic inter-conversion between azimuthally- and radially-polarised modes

Rotation of the transverse optical spin during propagation

Validation of theory and simulations through experiments

Abstract

Due to the inhomogeneous polarisation across the beam profile, cylindrical vector beams interact with optically active media in a complex manner. Here, we analyse evolution of polarisation of cylindrical vector beams propagating in an isotropic optically-active medium. After identifying polarisation normal modes of three-dimensional electromagnetic fields, we predict periodic inter-conversion between azimuthally- and radially-polarised modes of the beams accompanied by rotation of the transverse optical spin and pulsing field during the propagation. Theory and simulations are validated by experimental observations. The observed effects maybe important for imaging in biological chiral media, enhanced chiral sensing and enantioselective spectroscopy, nonlinear optics in chiral media, and generally enhanced spin-orbit coupling and nanoscale vector field engineering.