Enhanced transmission modulation based on dielectric metasurfaces loaded with graphene

Abstract

We present a hybrid graphene dielectric metasurface design to achieve strong tunable and modulated transmission at near-infrared (near-IR) frequencies. The proposed device is constituted by periodic pairs of asymmetric silicon nanobars placed over a silica substrate. An one-atom-thick graphene sheet is positioned between the nanobars and the substrate. The in-plane electromagnetic fields are highly localized and enhanced with this all-dielectric metasurface due to its zero Ohmic losses at near-IR wavelengths. They strongly interact with graphene and couple to its properties. Sharp Fano transmission is obtained at the resonant frequency of this hybrid all-dielectric metasurface configuration due to the cancelation of the electric and magnetic dipole responses at this frequency point. The properties of the graphene monolayer flake can be adjusted by tuning its Fermi energy or chemical potential, leading to different doping levels and, equivalently, material parameters. As a result, the Q factor and the Fano resonant transmission spectrum of the proposed hybrid system can be efficiently tuned and controlled due to the strong light graphene interaction. Higher than 60 percent modulation in the transmission coefficient is reported at near-IR frequencies. The proposed hybrid graphene/dielectric nanodevice has compact footprint, ultrafast speed, and can be easily integrated to the current CMOS technology. These features would have promising applications to near-IR tunable filters, faster optical interconnects, efficient sensors, switches, and amplitude modulators.