RESONANCE FLUORESCENCE-SPECTRUM OF A 2-LEVEL ATOM DRIVEN BY A BICHROMATIC FIELD IN A SQUEEZED VACUUM

The steady-state resonance fluorescence spectrum of a two-level atom d riven by a bichromatic field in a broadband squeezed vacuum is studied . When the carrier frequency of the squeezed vacuum is tuned to the fr equency of the central spectral line, anomalous spectral features, suc h as hole burning and dispersive profiles, can occur at the central li ne. We show that these features appear for wider, and experimentally m ore convenient, ranges of the parameters than in the case of monochrom atic excitation. ?he absence of a coherent spectral component at the c entral line makes any experimental attempt to observe these features m uch easier. We also discuss the general features of the spectrum. When the carrier frequency of the squeezed vacuum is tuned to the first od d or even sidebands, the spectrum is asymmetric and only the sidebands an sensitive to phase. For appropriate choices of the phase the linew idths or only the odd or even sidebands can be reduced. A dressed-stal e interpretation is provided.