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

Abstract

Following the recent approach [Phys. Rev. Lett. 119, 073901 (2017); New J. Phys., 19, 123014 (2017)], we refine and accomplish a general scheme for the unified description of momentum and angular momentum of the light fields in complex material media. Equations for the canonical (orbital) and spin linear momenta, as well as the orbital and spin angular momenta are presented for a lossless inhomogeneous dispersive medium in a compact form, which is analogous to the Brillouin relationship for the energy. The results are applied to a surface plasmon-polariton field. The microscopic calculations support the phenomenological expectations. Our refined general scheme describes correctly the known unusual properties of the surface plasmon-polariton associated with transverse spin and magnetization momentum. Moreover, it predicts a singular momentum contribution sharply localized at the metal–dielectric interface, which is confirmed by the microscopic analysis. Our results can be useful for the optical systems employing structured light, especially in microoptics, plasmophotonics, optical sorting and micromanipulation.