Comparison of gold- and graphene-based resonant nano-structures for terahertz metamaterials and an ultra-thin graphene-based modulator

TL;DR

This paper compares graphene- and gold-based resonant nano-structures for terahertz metamaterials, revealing graphene's potential for deeply subwavelength resonances and demonstrating an ultra-thin graphene-based terahertz modulator with over 75% modulation depth.

Contribution

It introduces a detailed comparison of graphene and gold resonators and presents a novel multi-layer graphene metamaterial modulator for terahertz frequencies.

Findings

Graphene resonators achieve deeply subwavelength resonances due to large kinetic inductance.

Graphene's resonance strength is reduced by higher dissipative losses.

The proposed graphene-based modulator achieves over 75% modulation depth.

Abstract

Graphene exhibits unique material properties and in electromagnetic wave technology, it raises the prospect of devices miniaturized down to the atomic length scale. Here we study split-ring resonator metamaterials made from graphene and we compare them to gold-based metamaterials. We find that graphene's huge reactive response derived from its large kinetic inductance allows for deeply subwavelength resonances, although its resonance strength is reduced due to higher dissipative loss damping and smaller dipole coupling. Nevertheless, tightly stacked graphene rings may provide for negative permeability and the electric dipole resonance of graphene meta-atoms turns out to be surprisingly strong. Based on these findings, we present a terahertz modulator based on a metamaterial with a multi-layer stack of alternating patterned graphene sheets separated by dielectric spacers. Neighbouring graphene flakes are biased against each other, resulting in modulation depths of over 75% at a transmission level of around 90%.