 Mollow triplet

A central peak and two sidebands in the resonance fluorescence spectrum of a sufficiently strongly driven two-level system. The atom-field dressed state splitting produces sidebands near ${\omega }_L\pm \sqrt{{\Omega }^2+{\Delta }^2}$, where $\Omega$ is the resonant Rabi frequency. On resonance, changing the drive intensity changes the sideband spacing. Damping and detection conditions determine the resolved line shapes; the elastic coherent contribution must be distinguished from inelastic fluorescence.^[ref]

An experimental test drives an isolated transition with a narrow-band laser, collects fluorescence away from the intense drive beam, and scans a spectral analyzer while varying drive power. Resolving the sidebands requires spectral resolution and coupling frequency sufficient relative to the radiative linewidth. The predicted spectrum concerns transitions of the coupled system rather than simply the time dependence of its population.