Acoustic graphene plasmon nanoresonators for field enhanced infrared molecular spectroscopy

Abstract

Graphene plasmons (GPs) have shown strong potentials for many interesting applications, such as tunable metamaterials, optical modulators, molecular sensors, among others. When a graphene sheet is placed above a metallic substrate separated from graphene by a dielectric spacer, it can support a particularly interesting GP mode – acoustic graphene plasmons (AGPs). AGPs can provide strong electromagnetic field confinement and enhancement in the dielectric spacer, thus being promising candidates for field enhanced infrared molecular spectroscopy, particularly for probing small amounts of molecules. Here we propose and demonstrate numerically an AGP nanoresonator for sensing, consisting of a GP nanodisk separated from a metallic film by a nanometric spacer. Compared to conventional GPs, AGPs exhibit a much higher spontaneous emission rate, higher sensitivity to the dielectric permittivity inside the AGP nanoresonator and remarkable capability to enhance molecular vibrational fingerprints of nanoscale analyte samples. Our work opens novel avenues for sensing of ultra-small volume of molecules, as well as for studying enhanced light-matter interaction, e.g. strong coupling applications.