High Q-factor plasmonic resonators in continuous graphene excited by insulator-covered silicon gratings

Abstract

We propose a structure to excite plasmons in large-area continuous graphene films with insulator-covered sub-wavelength silicon gratings (ICSWSG). By numerical simulations we have demonstrated that, after adding a low-permittivity insulator underneath graphene, the graphene/gratings hybrid structure has a high Q-factor (∼66) and a sharp notch (with the full width at half maximum of ∼122 nm) in the transmission spectra at mid-infrared resonant wavelength. Furthermore, the plasmonic properties, e.g. the resonant wavelength, magnitude and Q-factor, can be tuned over a wide range via structure modulation and/or gating of graphene. The transmission dip is achieved over a wide angle range. Finally we demonstrate that such highly confined graphene plasmons could also be excited in graphene sandwiched between silicon gratings and a SiO₂ substrate.