Understanding the electromagnetic response of graphene/metallic nanostructures hybrids of different dimensionality

TL;DR

This paper investigates the electromagnetic responses of hybrid graphene/metallic nanostructures, revealing distinct physical mechanisms for plasmon modes and demonstrating their potential for tunable plasmonic devices.

Contribution

It provides a detailed analysis of the interaction mechanisms of far-field light with high-momentum plasmon modes in graphene-metal hybrids, highlighting differences between GPs and SPPs.

Findings

Identified two physical mechanisms for graphene plasmons: cavity confinement and grating coupling.

Discovered that under certain conditions, different systems can exhibit similar behaviors.

Showed that hybrids produce large, electrically tunable field enhancements.

Abstract

Plasmonic excitations such as surface-plasmon-polaritons (SPPs) and graphene-plasmons (GPs), carry large momenta and are thus able to confine electromagnetic fields to small dimensions. This property makes them ideal platforms for subwavelength optical control and manipulation at the nanoscale. The momenta of these plasmons are even further increased if a scheme of metal-insulator-metal and graphene-insulator-metal are used for SPPs and GPs, respectively. However, with such large momenta, their far-field excitation becomes challenging. In this work, we consider hybrids of graphene and metallic nanostructures and study the physical mechanisms behind the interaction of far-field light with the supported high momenta plasmon modes. While there are some similarities in the properties of GPs and SPPs, since both are of the plasmon-polariton type, their physical properties are also distinctly different. For GPs we find two different physical mechanism related to either GPs confined to isolated cavities, or large area collective grating couplers. Strikingly, we find that although the two systems are conceptually different, under specific conditions they can behave similarly. By applying the same study to SPPs, we find a different physical behavior, which fundamentally stems from the different dispersion relations of SPPs as compared to GPs. Furthermore, these hybrids produce large field enhancements that can also be electrically tuned and modulated making them the ideal candidates for a variety of plasmonic devices.