Resonance Scattering and Absorption of the E-Polarized Plane Wave by Graphene Strip On-Substrate Grating

We analyze numerically the E-polarized plane wave scattering and absorption by an infinite grating made of graphene strips lying on a flat dielectric substrate. Our instrument is a meshless full-wave code, built using the analytical regularization of the dual series equations, based on the use of Discrete Inverse Fourier Transform. This technique casts the scattering problem to a Fredholm 2nd-kind matrix equation for the unknown amplitudes of the scattered field Floquet harmonics and thus guarantees the convergence. Our computations demonstrate that such a metasurface is highly frequency-selective. If the elementary cell size and substrate thickness are in tens of microns, then the resonance frequencies of such a periodic cavity are in the terahertz range. They are of two different families-low-Q natural modes of the substrate and ultrahigh-Q lattice modes of the whole grating.