Resonance fluorescence spectra of three-level atoms in a squeezed vacuum.

Abstract

The fluorescence field from one of the two allowed transitions in a three level atom can sense squeezed fluctuations of a vacuum field coupled to the other transition. A study is made of fluorescence spectra of three-level atoms in lambda, vee and cascade configurations, strongly driven by two laser fields, both tuned to one photon resonance. Only one of the two one-photon transitions is coupled to a narrow-band squeezed vacuum field, the bandwidth being much smaller than the difference in the atomic transition frequencies, though much larger than atomic decay rates and Rabi frequencies of the driving fields. It is found that in all configurations the spectra consist of five lines, one central and two pairs of sidebands, with intensities and widths which are strongly influenced by the squeezed vacuum. However, only the central component and the outer sidebands exhibit a dependence on the squeezing phase. The spectral features are explained in terms of the dressed-atom model for the system. It is shown that the coherent mixing of the atomic states by the strong driving fields modifies transition rates between the dressed states resulting in the phase dependence of the spectral features.