SHIFT OF THE SUBHARMONIC RESONANCES AND SUPPRESSION OF FLUORESCENCE IN A 2-LEVEL ATOM DRIVEN BY A BICHROMATIC FIELD

We study the behavior of a two-level atom that is driven by a bichroma tic field consisting of a strong resonant component and a weaker tunab le component. In addition to the splitting of the energy levels (the m ultiphoton AC Stark effect), we find that the weaker component also sh ifts the subharmonic resonances, an effect we attribute to a dynamic S tark shift. When the weaker component is tuned to a shifted resonance, no fluorescence occurs at either the frequency of the strong componen t or the three-photon mixing frequency. Results are obtained with nume rical techniques and explained in terms of the dressed-atom model of t he system. (C) 1998 Optical Society of America [S0740-3224(98)01508-2] OCIS codes: 270.4180, 270.6620, 270.0270.