Enhancing the light–matter coupling using a 3D-graphene-dielectric-micro-cavity

We propose a 3D-graphene-cube cavity, consisting of a micro-cube and a planar graphene sheet covering a dielectric substrate, to improve the electromagnetic coupling between a quantum emitter (QE) and the surface plasmon (SP) field. The cavity supports two electromagnetic bands: one corresponding to surface plasmons (SPs) on the graphene sheet (the higher-frequency band), and the other arising from SP-field reflections between the base of the micro-cube and the graphene sheet (the lower-frequency band). Due to the resonant coupling between the QE and these plasmonic cavity modes, its relaxation rate is significantly enhanced compared to its free-space value, and the population dynamics can exhibit reversible behavior. By varying specific cavity parameters, the coupling with the low-frequency plasmonic band can be enhanced while keeping the coupling with the high-frequency band nearly constant. Furthermore, we demonstrate that, for certain values of these parameters, the quantum emitter population can be trapped in the excited state, forming a bound state within the environment. Our results could enable a novel, to the best of our knowledge, strategy for developing chip-scale quantum plasmonic devices.