The spin-orbit interaction and the spin-spin interaction of photons in an inhomogeneous medium

TL;DR

This paper explores how polarized light propagates in inhomogeneous media, revealing that both spin-orbit and spin-spin interactions influence photon trajectories, leading to small deflections beyond the known spin Hall effect.

Contribution

It introduces the concept of spin-spin interaction affecting photon propagation in inhomogeneous media, a novel addition to the understanding of light-matter interactions.

Findings

Photon trajectories are affected by spin-spin interaction.

Small deflections occur along the inhomogeneity gradient.

The deflection differs from the spin Hall effect of photons.

Abstract

By means of the optical metric, we investigate the propagation of a polarized light in an inhomogeneous medium in this paper. We find that the evolution of photons is affected by the spin-spin interaction of photons, besides the spin-orbit interaction. Due to the spin-spin interaction, there is a small deflection of the ray trajectory of the polarized light along the direction of the inhomogeneity gradient of the medium. It is different from the transverse deflection described by the spin Hall effect of photons.