Tailoring Strong Multimode Interaction in a Graphene-based Coupled Plasmonic System

We theoretically investigate the hybrid coupling among graphene surface plasmons (GSP) and magnetic polaritons (MP) in a coupled three-mode system. Numerical results reveal that the superposition of the resonance peaks generated by plasmonic hybridization can achieve multispectral perfect absorption, and these results are verified by coupled oscillator model. The electromagnetic energy at different resonance frequencies can be selectively localized at different positions of the nanostructure. The GSP mode can interact with two MP modes by dynamically tuning the chemical potential of graphene, resulting in two distinct Rabi splitting phenomena with mode splitting energies of 10.3 meV and 16.5 meV, respectively. In particular, additional MP modes can be introduced by etching more slits with different depths in silver grating, which also leads to more spectral splitting and complicated mode coupling. The presented results should be useful for multimode interaction studies, and have potential applications in highly tunable graphene-based plasmonic devices.