Dispersion, propagation, and transverse spin of surface plasmon polaritons in a metal-chiral-metal waveguide

Abstract

Chiral media that exist ubiquitously in both nature and artificial metamaterials have exotic optical properties. The influence of chirality on the features of surface plasmon polaritons (SPPs) in a metal-chiral-metal plasmonic waveguide is revealed under realistic material parameters. A universal dispersion relation is derived, which covers the achiral metal-insulator-metal case. When the core of a symmetric waveguide is sufficiently thin, the introduction of chirality will weaken the cutoff effect which usually occurs in the antisymmetric surface plasmon mode. It is found that in the chiral case, the surface plasmon resonance frequency is slightly raised and that the propagation is enhanced. It is also demonstrated that chirality might modulate the transverse spin effect of SPPs in the waveguide. This work may enrich the plasmonics theory which is of great importance for nanophotonic devices.