Spin and momentum of the light fields in inhomogeneous dispersive media with application to surface plasmon-polariton waves

TL;DR

This paper refines a unified theoretical framework for describing the momentum and angular momentum of light in complex media, applying it to surface plasmon-polariton waves and revealing novel localized momentum effects at interfaces.

Contribution

It advances the theoretical understanding of light's momentum in inhomogeneous dispersive media, including new predictions of localized interface momentum contributions.

Findings

Correctly describes transverse spin and magnetization momentum of SPPs

Predicts a singular momentum localized at the metal-dielectric interface

Microscopic calculations support the phenomenological model

Abstract

Following to the recently published approach [Phys. Rev. Lett. 119, 073901 (2017); New J. Phys., 123014 (2017)], we refine and accomplish the general scheme for the unified description of the momentum and angular momentum in complex media. The equations for the canonical (orbital) and spin linear momenta, orbital and spin angular momenta in a lossless inhomogeneous dispersive medium are presented in the compact form analogous to the Brillouin's relation for the energy. The results are applied to the surface plasmon-polariton (SPP) field, and the microscopic calculations support the phenomenological expectations. The refined general scheme correctly describes the unusual SPP properties (transverse spin, magnetization momentum) and additionally predicts the singular momentum contribution sharply localized at the metal-dielectric interface, which is confirmed by the microscopic analysis. The results can be useful in optical systems employing the structured light, especially for microoptics, plasmophotonics, optical sorting and micromanipulation.