Controlling spoof plasmons in a metal grating using graphene surface plasmons

TL;DR

This paper demonstrates how placing a doped graphene sheet near a metallic grating allows for tunable control of spoof plasmon dispersion in the THz to mid-IR range, enabling applications in absorption and sensing.

Contribution

It introduces a semi-analytical model to control spoof plasmons via graphene, enhancing system versatility with less computational effort.

Findings

The system can act as a perfect absorber.

The system can be used as a sensor for alcohols.

Absorption frequency is tunable by geometry and Fermi energy.

Abstract

Spoof plasmons mimic noble metal plasmons. The equivalent of the plasma frequency is an energy scale imposed by the geometry of the metal grating upon which they propagate. In this paper we show that the dispersion of spoof plasmons in the THz can be controlled placing a doped graphene sheet on the proximity of a metallic grating, adding more versatility to this type of system. We develop a semi-analytical model, based on a perfect-metal diffraction grating. This model allows to reproduce well FDTD calculations for the same problem but with much less computer time. We discuss the optical properties of the system covering a spectral range spanning the interval from the THz to the mid-IR. It is shown that the system can be used as both a perfect absorber and a sensing device. For illustrating the latter property we have chosen different alcohols as analytes. The frequency at which perfect absorption appears can be controlled by the geometric parameters of the grating and by the value of the Fermi energy in graphene. The theoretical results predicted throughout this work can be verified experimentally in the future.