Coupling of Graphene Plasmonics Modes Induced by Near-Field Perturbation at Terahertz Frequencies

Abstract

The coupling between graphene surface plasmonic (GSP) modes and evanescent wave modes induced by near-field perturbation is investigated systematically in the grating-spacer-graphene hybrid system. Simulation results show that the near-field perturbation due to a small change of the geometrical structure disturbs the coupling characteristics, leading to the evolution of the absorption spectra and the spatial energy redistribution of GSP modes. By exploring the physical mechanism, the shift of the resonant absorption frequency can be quantified through the variation of the effective permittivity around graphene, while the first order evanescent wave in the grating plays a fundamental role in determining the absorbance in the coupling process. Further discussion indicates that the different penetration abilities of GSP wave into dielectric and metal grating contribute to the discrepancy of the energy distribution of GSP modes. Our study provides new physical insight and promotes a further step for the design of plasmonics devices at terahertz frequencies.