Stokes-vector evolution in a weakly anisotropic inhomogeneous medium

TL;DR

This paper derives a generalized equation for the evolution of the Stokes vector in weakly anisotropic, inhomogeneous media, linking optical polarization dynamics to spin precession equations and applying it to magnetized plasma.

Contribution

It introduces a new, comprehensive equation for Stokes vector evolution that accounts for complex media features and connects optical polarization with relativistic spin precession.

Findings

Equation generalizes previous models for stratified media

Describes polarization evolution with spin precession analogies

Applied to analyze polarization in magnetized plasma

Abstract

Equation for evolution of the four-component Stokes vector in weakly anisotropic and smoothly inhomogeneous media is derived on the basis of quasi-isotropic approximation of the geometrical optics method, which provides consequent asymptotic solution of Maxwell equations. Our equation generalizes previous results, obtained for the normal propagation of electromagnetic waves in stratified media. It is valid for curvilinear rays with torsion and is capable to describe normal modes conversion in the inhomogeneous media. Remarkably, evolution of the Stokes vector is described by the Bargmann-Michel-Telegdi equation for relativistic spin precession, whereas the equation for the three-component Stokes vector resembles the Landau-Lifshitz equation for spin precession in ferromegnetic systems. General theory is applied for analysis of polarization evolution in a magnetized plasma. We also emphasize fundamental features of the non-Abelian polarization evolution in anisotropic inhomogeneous media and illustrate them by simple examples.