Nanowires-assisted excitation and propagation of mid-infrared surface plasmon polaritons in graphene

We investigate the excitation and propagation of surface plasmon polaritons in a novel graphene hybrid photonic nanostructure, which consists of a graphene sheet and a dielectric layer with partly etched nanowires coated on the silicon substrate. The simulation and analytical results show that the mid-infrared plasmonic wave can be generated in the graphene sheet by normally incident light due to the satisfaction of the wavevector matching condition. Especially, we find that the plasmonic wavelength and spectral width are determined by the width, pitch, and refractive index of the dielectric nanowires, as well as the layer number and the Fermi level of graphene sheet. The analytical calculations agree well with the finite-difference time-domain simulations. These results would provide an new avenue toward the excitation of graphene plasmonics for the manipulation of mid-infrared light at nanoscale.