Magnetic modulation of surface plasmon modes in magnetoplasmonic Metal-Insulator-Metal cavities

Abstract

The dispersion relation of surface plasmon polaritons (SPPs) can be modified by the application of an external magnetic field. In particular, when applied parallel to the interface but perpendicular to the SPP propagation direction, it modifies the SPP wavevector and introduces non - reciprocity in the dispersion relation. So far, the most often analyzed configuration consists of a single metal - dielectric interface where a magnetic element is introduced to increase the magneto - optic response, namely a ferromagnetic metal in a noble metal/ferromagnetic metal multilayer or a ferromagnetic dielectric. However, very few studies have been devoted to more complex configurations composed of interacting interfaces. Metal - Insulator - Metal (MIM) structures are very interesting as they can be used as plasmonic waveguides, strongly squeezing the SPP field into the dielectric core and allowing the realization of nanocavities with extremely small mode volumes.