Integral Equation Analysis of Plane Wave Scattering by Coplanar Graphene-Strip Gratings in the THz Range

TL;DR

This paper introduces a novel numerical method for analyzing plane wave scattering by graphene-strip gratings in the THz range, revealing surface plasmon resonances and their dependence on material parameters, with implications for tunable devices.

Contribution

A new computational approach based on surface impedance and integral equations for accurately modeling graphene grating scattering in the THz range.

Findings

Larger graphene relaxation times increase surface plasmon resonances.

Increasing chemical potential shifts plasmon resonance frequencies.

Few graphene strips can reproduce Rayleigh anomalies.

Abstract

The plane wave scattering and absorption by finite and infinite gratings of free-space standing infinitely long graphene strips are studied in the THz range. A novel numerical approach, based on graphene surface impedance, hyper-singular integral equations, and the Nystrom method, is proposed. This technique guarantees fast convergence and controlled accuracy of computations. Reflectance, transmittance, and absorbance are carefully studied as a function of graphene and grating parameters, revealing the presence of surface plasmon resonances. Specifically, larger graphene relaxation times increases the number of resonances in the THz range, leading to higher wave transmittance due to the reduced losses; on the other hand an increase of graphene chemical potential up-shifts the frequency of plasmon resonances. It is also shown that a relatively low number of graphene strips (>10) are able to reproduce Rayleigh anomalies. These features make graphene strips good candidates for many applications, including tunable absorbers and frequency selective surfaces.