PHASE-DEPENDENT FLUORESCENCE LINEWIDTH NARROWING IN A 3-LEVEL ATOM DAMPED BY A FINITE-BANDWIDTH SQUEEZED VACUUM

We examine subnatural phase-dependent linewidths in the fluorescence s pectrum of a three-level atom damped by a narrow-bandwidth squeezed va cuum in a cavity. Using the dressed-atom model approach of a strongly driven three-level cascade system, we derive the master equation of th e system from which we obtain simple analytical expressions for the fl uorescence spectrum. We show that the phase effects depend on the band widths of the squeezed vacuum and the cavity relative to the Rabi freq uency of the driving fields. When the squeezing bandwidth is much larg er than the Rabi frequency, the spectrum consists of five lines with o nly the central and outer sidebands dependent on the phase. For a sque ezing bandwidth much smaller than the Rabi frequency the number of lin es in the spectrum and their phase properties depend on the frequency at which the squeezing and cavity modes are centered. When the squeezi ng and cavity modes are centered on the inner Rabi sidebands, the spec trum exhibits five lines that are completely independent of the squeez ing phase with only the inner Rabi sidebands dependent on the squeezin g correlations. Matching the squeezing and cavity modes to the outer R abi sidebands leads to the disappearance of the inner Rabi sidebands a nd a strong phase dependence of the central line and the outer Rabi si debands. We find that in this case the system behaves as an individual two-level system that reveals exactly the noise distribution in the i nput squeezed vacuum. [S1050-2947(97)00111-X].