Theoretical analysis of graphene plasmon cavities

Abstract Unprecedented physical properties make graphene a very promising plasmonic candidate material from the terahertz to mid-infrared frequencies. However, a theoretical model for graphene plasmon cavities has not been fully established. In this work, we analyse the graphene surface plasmon polaritons supported on silicon carbide or metallic cavities. We derive an analytical expression for the dispersion relation of graphene plasmon waves in a multilayer system, providing a useful tool to illustrate the dependence on the cavity's geometric properties. The results show that the analytical description can precisely predict the excitation of cavity graphene plasmon waves. Complete absorption can be achieved under certain parameters, which can be predicted precisely using two Fabry–Perot models. We further show that the interaction of surface plasmon polaritons with surface phonon polaritons can be used to tune the cavity resonances. The tunability of the Fermi energy and the geometric parameters of the cavities make for flexible system design. High enhancement (∼4000) and extraordinary compression (∼λ0/400) of graphene plasmon waves are also realized under certain conditions. These findings make this an ideal setup for molecular sensing, pushing the potential for enhanced, broadly tunable spectroscopy into the mid-infrared, while also offering distinct advantages for integrated optics.