Spontaneous emission spectrum of a two-level atom in a very high Q cavity

TL;DR

This paper derives exact spectra for a two-level atom coupled to a high-Q cavity, revealing photon emission characteristics and their relation to classical fluorescence spectra, with implications for quantum optics.

Contribution

It provides a novel exact analytical method for calculating spontaneous emission spectra in atom-cavity systems with arbitrary linewidths and detunings.

Findings

Photons are emitted at the cavity frequency when cavity linewidth is much lower than atomic linewidth.

The spectra are linked to fluorescence spectra under classical driving.

The classical counterpart simplifies understanding of quantum emission phenomena.

Abstract

In this paper we consider an initially excited two-level system coupled to a monomode cavity, and compute exact expressions for the spectra spontaneously emitted by each system in the general case where they have arbitrary linewidths and frequencies. Our method is based on the fact that this problem has an easily solvable classical counterpart, which provides a clear interpretation of the evidenced phenomena. We show that if the cavity linewidth is much lower than the atomic linewidth, photons are emitted at the cavity frequency, even if the atom and the cavity are strongly detuned. We also study the links between the spontaneous emission spectra and the fluorescence spectra emitted when the atom is driven by a classical field of tunable frequency.