Quantum versus Classical Descriptions of Spontaneous Emission in Nanophotonic Cavities

TL;DR

This paper compares quantum and classical models of spontaneous emission in nanophotonic cavities, revealing differences influenced by material properties and cavity design, with convergence in ideal lossless cases.

Contribution

It derives a unified expression for emission rate enhancement considering dispersive and lossy cavities, highlighting conditions where quantum and classical models agree or differ.

Findings

Quantum and classical emission predictions differ in typical nanophotonic cavities.

The ratio of quantum to classical emission rates depends on material dispersion and cavity morphology.

Quantum and classical descriptions converge in lossless, non-dispersive dielectric and low-loss plasmonic cavities.

Abstract

Here, we demonstrate that quantum and classical descriptions generally yield different results for the spontaneous emission in nanophotonic cavities. Starting from the quantized single-mode field in a general context of dispersive and lossy cavities, we derive the expression for emission rate enhancement as well as key relevant parameters such as mode volume and quality factor. For general nanophotonic cavities, this ratio of the quantum to the classical description is typically below unity and varies with the material dispersion properties, scattering-to-absorption ratio and morphology of the cavity. Notably, the two descriptions converge for lossless, non-dispersive dielectric cavities and for noble-metal plasmonic cavities with sufficiently low scattering losses.