Abstract
We analyze the fluorescence and absorption spectra of a two-level atom driven by a bichromatic field with frequencies and , separated by -=2δ, and Rabi frequencies (at resonance) 2 and 2 such that their ratio α=/<1. We focus on the case of close to the atomic frequency and near the Rabi sideband frequency +2; the detunings are denoted by =- and =+2-. We find that the spectra depend critically on the detuning : For large , the fluorescence spectrum consists of the well known Mollow triplet, centered at ; for smaller (but nonzero) , the spectrum is composed of a triplet at together with doublets near the sideband frequencies ±2. However, when =0 (and α≪1), the spectrum consists of a doublet centered at and triplets at ±2: there is then no fluorescence at . As α increases, additional triplet structures appear in the spectrum at frequencies ±2n with intensities proportional to , n≳1, and a line reappears at , with intensity proportional to . The absorption by the system of a weak probe beam is also strongly dependent on the detuning, and the spectrum is composed of emission-dispersion-absorption features located near and ±2n. An analysis in the dressed-atom picture is presented which explains the physical origin of all these features, in both fluorescence and absorption. © 1996 The American Physical Society.
- Received 29 June 1995
DOI:https://doi.org/10.1103/PhysRevA.53.4275
©1996 American Physical Society