Spontaneous Emission Spectra and Quantum Light-Matter Interactions from a Strongly-Coupled Quantum Dot Metal-Nanoparticle System

TL;DR

This paper explores the quantum optical behavior of a single photon emitter near a metal nanoparticle, revealing strong coupling effects and complex emission spectra at room temperature using a rigorous quantum electrodynamics approach.

Contribution

It introduces a non-dipole, Green function-based analysis of quantum dot-metal nanoparticle systems, demonstrating observable strong coupling effects in spontaneous emission spectra.

Findings

Pronounced Purcell factors and Lamb shifts without dipole approximation.

Observation of vacuum Rabi triplet or quartet in emission spectra at room temperature.

Strong coupling signatures persist despite non-radiative decay channels.

Abstract

We investigate the quantum optical properties of a single photon emitter coupled to a finite-size metal nanoparticle using a photon Green function technique that rigorously quantizes the electromagnetic fields. We first obtain pronounced Purcell factors and photonic Lamb shifts for both a 7-nm and 20-nm radius metal nanoparticle, without adopting a dipole approximation. We then consider a quantum-dot photon emitter positioned sufficiently near to the metal nanoparticle so that the strong coupling regime is possible. Accounting for non-dipole interactions, quenching, and photon transport from the dot to the detector, we demonstrate that the strong coupling regime should be observable in the far-field spontaneous emission spectrum, even at room temperature. The emission spectra show that the usual vacuum Rabi doublet becomes a rich spectral triplet or quartet with two of the four peaks anticrossing, which survives in spite of significant non-radiative decays. We discuss the emitted light spectrum and the effects of quenching for two different dipole polarizations.