Asymmetric two-level two-level resonance fluorescence spectra and dressed state populations in a squeezed vacuum

The authors calculate the resonance fluorescence spectrum of a two-level atom interacting with a resonant classical applied field and a squeezed vacuum for general values of the squeezing phase. They find that the spectra are asymmetric under the following conditions: (i) the Rabi frequency must not be too large and (ii) the squeezing phase should be of athe order pi /2. Large asymmetries are obtainable, even if the three peaks of the spectrum are clearly resolved. An interpretation is provided by means of a dressed state analysis. Under conditions (i) and (ii), they also find that very large differences in the dressed state populations can occur.