Surface plasmon enhanced THz spontaneous emission near metal-cored wires coated with graphene

Abstract

This work deals with the theoretical study of the spontaneous emission of a point dipole source placed near a cylindrical structure composed of a central metallic core and a dielectric shell covered with graphene. We show that the spontaneous emission rate is dominated by coupling into surface plasmon (SP) modes on graphene, which present high values of the propagation constant along the cylinder symmetry axis. When the dielectric shell thickness is reduced, the plasmon dispersion is modified into a linear dependence and the modal SP propagation constant is further incremented, involving an improved field confinement. This effect is manifested as a redshift of the emission frequency spectrum for each individual cylindrical harmonic mode. We propose a simple model that provides us a link between the dispersion characteristics and maximum emission rate for each SP cylindrical mode.