Strong Light-Matter Interaction in Quantum Emitter/Metal Hybrid Nanostructures

Surface plasmon polaritons (SPPs) are spatially confined electromagnetic field modes at a metal-dielectric interface capable of generating intense near-field optical forces on ultrafast time scales. Within the field of photonics, SPPs carry significant potential for guiding and manipulating light on the nanoscale. The intense SPP fields substantially enhance light-matter interactions with quantum emitters (QEs). Thus, hybrid systems comprised of SPP resonators and various types of QEs constitute key components of the modern photonics applications. Recent advances in nanotechnology have enabled fabrication of high quality QE/metal hybrid nanostructures, in which several aspects of light matter interactions, including those in the quantum regime have been demonstrated and extensively studied. The present Perspective explores the central phenomenon in light-matter interaction in emitter/metal hybrid nanostructures, namely, the strong dipole coupling between QEs and SPPs, particularly between excitons (Xs) and SPPs. We provide a concise description of the relevant background physics and discuss the dynamics of the coupled QE-SPP modes. We also review the extent to which the strong QE-SPP coupling has been enhanced to reach the challenging but fascinating fundamental quantum mechanical limit of a single QE coupled to a single SPP mode. Studies have demonstrated that these remarkable hybrid nanostructures supporting single QE-SPP coupled mode can potentially open up diverse exciting possibilities like single-molecule sensing, nanoscale light sources, single-photon emitters, and all-optical transistors.