RESONANCE FLUORESCENCE-SPECTRA OF 3-LEVEL ATOMS IN A SQUEEZED VACUUM

The fluorescence field from one of the two allowed transitions in a th ree-level atom can sense squeezed fluctuations of a vacuum field coupl ed to the other transition. We examine the fluorescence spectra of str ongly driven three-level atoms in Lambda, V, and cascade configuration s in which one of the two one-photon transitions is coupled to a finit e-bandwidth squeezed vacuum field, when the bandwidth is much smaller than the difference in the atomic transition frequencies, though much larger than atomic decay rates and Rabi frequencies of the driving fie lds. The driving fields are on one-photon resonance, and the squeezed vacuum field is generated by a degenerate parameter oscillator. Detail s are only given for the Lambda configuration. The extension to the V and cascade configurations is straightforward. We find that in all con figurations the fluorescence spectra of the transition not coupled to the squeezed vacuum field are composed of five lines, one central and two pairs of sidebands, with intensities and widths strongly influence d by the squeezed vacuum field. However, only the central component an d the outer sidebands exhibit a dependence on the squeezing phase. We also examine the fluorescence spectrum for the cascade configuration w ith a squeezed vacuum field on resonance with the two-photon transitio n between the ground and the most excited states and now generated by a nondegenerate parametric oscillator. In this case, where the squeeze d vacuum field can be made coupled to both transitions, all spectral l ines depend on the squeezing phase. The spectral features are explaine d in terms of the dressed-atom model of the system. We show that the c oherent mixing of the atomic states by the strong driving fields modif ies transition rates between the dressed states, which results in the selective phase dependence of the spectral features.