Plasmons and near-field amplification in double-layer graphene

TL;DR

This paper investigates the optical properties of double-layer graphene, revealing conditions for near-field amplification through plasmon modes, which could enable tunable near-field amplification or switching devices.

Contribution

It provides a detailed analysis of plasmon modes and near-field amplification in double-layer graphene, including the effects of layer density and chemical potential differences.

Findings

Zero reflection energy leads to amplified transmitted modes.

Amplification depends on in-phase or out-of-phase plasmon modes.

Potential for tunable near-field amplifiers or switches.

Abstract

We study the optical properties of double-layer graphene for linearly polarized evanescent modes and discuss the in-phase and out-of-phase plasmon modes for both, longitudinal and transverse polarization. We find a energy for which reflection is zero, leading to exponentially amplified transmitted modes similar to what happens in left-handed materials. For layers with equal densities $n=10^{12}$cm$^{-2}$, we find a typical layer separation of $d\approx500\mu$m to detect this amplification for transverse polarization which may serve as an indirect observation of transverse plasmons. When the two graphene layers lie on different chemical potentials, the exponential amplification either follows the in-phase or out-of-phase plasmon mode depending on the order of the low- and high-density layer. This opens up the possibility of a tunable near-field amplifier or switch.