Tuning Light–Matter Interactions with Mid-Infrared Plasmonic Coaxial Apertures

Abstract

Thin plasmonic coaxial apertures have unique optical properties, including extraordinary light transmission and confinement, that can enhance light–matter interactions and can be applied for sensing applications. Here, we use finite-difference time-domain simulations to investigate the mid-infrared optical response of coaxial aperture arrays, consisting of a combination of disk arrays and perforated films of periodically arranged holes. We find that the plasmon response of these arrays is governed by the disk size with little influence from the hole size, with surface plasmon excitation around the circumference of the disks mediating extraordinary optical transmission and strong near-field enhancements. The simulations also predict that light–matter coupling with the vibrational modes of a poly(methyl methacrylate) film placed inside the coaxial apertures can be tuned from weak to strong by adjusting the thickness of the coaxial aperture array’s metal film. Such open structures that can promote tailored light–matter interactions are therefore attractive target platforms for plasmon-enhanced sensing and polaritonic chemistry.