Electrical Switching of Infrared Light Using Graphene Integration with Plasmonic Fano Resonant Metasurfaces

Graphene has emerged as a promising optoelectronic material because its optical properties can be rapidly and dramatically changed using electric gating Graphene's weak optical response especially in the infrared part of the spectrum, remains the key challenge to developing practical graphene-based optical devices such as modulators, infrared detectors, and tunable reflect-arrays Here it is experimentally and theoretically demonstrated that a plasmonic metasurface with two Fano resonances can dramatically enhance the interaction of infrared light with single layer graphene: Graphene's plasmonic response in the Pauli blocking regime is shown to cause strong spectral shifts of the Fano resonances without inducing additional nonradiative losses. It is shown that such electrically controllable spectral shift, combined with the narrow spectral width of the metasurface's Fano resonances, enables reflectivity modulation by nearly an order of magnitude. We also demonstrate that metasurface-based enhancement of the interaction between graphene and infrared light can be utilized to extract one of the key optical parameters of graphene: the free carrier scattering rate. Numerical simulations demonstrate the,possibility of strong active modulation of the phase of the reflected light while keeping the reflectivity nearly constant, thereby paving the way to tunable infrared lenses and beam steering devices based on electrically controlled graphene integrated with resonant metasurfaces.