Tunable giant Purcell enhancement of quantum light emitters by means of acoustic graphene plasmons

TL;DR

This paper demonstrates how acoustic graphene plasmons can be used to achieve highly tunable, giant Purcell enhancements for various quantum emitters, enabling improved quantum communication and information processing devices.

Contribution

It introduces a novel cavity design utilizing acoustic graphene plasmons for tunable, large Purcell enhancements across the infrared spectrum, with detailed FDTD analysis and practical implications.

Findings

Achieved Purcell enhancement factors up to 10^9 for certain transitions.

Demonstrated tunability of Purcell enhancement via electrostatic gating of graphene.

Achieved high quantum efficiencies up to 95% at telecom wavelengths.

Abstract

Inspired by the remarkable ability of plasmons to boost radiative emission rates, we propose leveraging acoustic graphene plasmons (AGPs) to realize tunable, giant Purcell enhancements for single-photon, entangled-photon, and multipolar quantum emitters. These AGPs are localized inside a cavity defined by a graphene sheet and a metallic nanocube and filled with a dielectric of thickness of a few nanometers and consisting of stacked layers of 2D materials, containing impurities or defects that act as quantum light emitters. Through finite-difference time domain (FDTD) calculations, we show that this geometry can achieve giant Purcell enhancement factors over a large portion of the infrared (IR) spectrum, up to 6 orders of magnitude in the mid-IR and up to 4 orders of magnitude at telecommunications wavelengths, reaching quantum efficiencies of 95\% and 89\%, respectively, with high-mobility graphene. We obtain Purcell enhancement factors for single-photon electric dipole (E1), electric quadrupole (E2), and electric octupole (E3) transitions and two-photon spontaneous emission (2PSE) transitions, of the orders of $10^{4}$, $10^{7}$, $10^{9}$, and $10^9$, respectively, and a quantum efficiency of 79\% for entangled-photon emission with high-mobility graphene at a wavelength of $\lambda=1.55$ $\mu$m. Importantly, AGP mode frequencies depend on the graphene Fermi energy, which can be tuned via electrostatic gating to modulate fluorescence enhancement in real time. As an example, we consider the Purcell enhancement of spontaneous single- and two-photon emissions from an erbium atom inside single-layer (SL) WS$_2$. Our results could be useful for electrically tunable quantum emitter devices with applications in quantum communication and quantum information processing.