Resonance fluorescence in the resolvent operator formalism

TL;DR

This paper derives the Mollow spectrum for a driven two-level atom using the resolvent operator formalism, demonstrating that the atomic linewidth remains largely unchanged even in strong fields.

Contribution

It introduces a new derivation method for the Mollow spectrum based on the resolvent operator, providing insights into linewidth behavior in strong-field regimes.

Findings

The natural linewidth remains essentially unmodified in strong fields.

The derived spectrum matches the classical Mollow spectrum.

The master equation accurately describes the atom-field system.

Abstract

The Mollow spectrum for the light scattered by a driven two-level atom is derived in the resolvent operator formalism. The derivation is based on the construction of a master equation from the resolvent operator of the atom-field system. We show that the natural linewidth of the excited atomic level remains essentially unmodified, to a very good level of approximation, even in the strong-field regime, where Rabi flopping becomes relevant inside the self-energy loop that yields the linewidth. This ensures that the obtained master equation and the spectrum derived matches that of Mollow.