Edge and waveguide THz surface plasmon modes in graphene micro-ribbons

TL;DR

This paper investigates and classifies surface plasmon modes in graphene micro-ribbons, highlighting the properties of waveguiding and edge modes, their separation, and the fundamental mode with minimal losses.

Contribution

It provides a detailed analysis of plasmon modes in graphene ribbons, identifying the fundamental edge mode and its loss characteristics, which advances understanding of graphene plasmonics.

Findings

Waveguide and edge modes are separated by a wavenumber gap.

The fundamental mode is an even-parity hybridized edge mode with lowest losses.

An optimal frequency exists where absorption losses are minimized.

Abstract

Surface plasmon modes supported by graphene ribbon waveguides are studied and classified. The properties of both modes with the field concentration within the ribbon area (waveguiding modes) and on the edges (edge modes) are discussed. The waveguide and edge modes are shown to be separated from each other by a gap in wavenumbers. The even-parity hybridized edge mode results to be the fundamental electromagnetic mode of the ribbon, possessing also the lowest losses. All the plasmonic modes in the ribbons have an optimum frequency, at which the absorption losses are minimum, due to competition between the plasmon confinement and the frequency dependence of absorption in graphene.