Electronically Tunable Perfect Absorption in Graphene

TL;DR

This paper demonstrates electronically tunable perfect light absorption in graphene nanostructures, achieving near-unity absorption efficiency by overcoming plasmon-photon mismatch through innovative nanophotonic design.

Contribution

The authors develop nanophotonic structures that enable high-efficiency, tunable perfect absorption in graphene, surpassing previous limitations of low absorption efficiency.

Findings

96.9% absorption at 1389 cm$^{-1}$

95.9% on/off modulation efficiency

Design based on critical coupling model

Abstract

Graphene nanostructures that support surface plasmons have been utilized to create a variety of dynamically tunable light modulators, motivated by theoretical predictions of the potential for unity absorption in resonantly-excited monolayer graphene sheets. Until now, the generally low efficiencies of tunable resonant graphene absorbers have been limited by the mismatch between free-space photons and graphene plasmons. Here, we develop nanophotonic structures that overcome this mismatch and demonstrate electronically tunable perfect absorption achieved with patterned graphenes covering less than 10% of the surface. Experimental measurements reveal 96.9% absorption in the graphene plasmonic nanostructure at 1,389 cm$^{-1}$, with an on/off modulation efficiency of 95.9% in reflection. An analytic effective surface admittance model elucidates the origin of perfect absorption, which is design for critical coupling between free-space modes and the graphene plasmonic nanostructures.