Quantum interference effects in resonance fluorescence and absorption spectra of a V-type three-level atom damped by a broadband squeezed vacuum

Abstract

The resonance fluorescence spectrum (RFS) and the absorption of a weak probe beam of a V-type three-level atom damped by a broadband squeezed vacuum and driven by a single coherent field which simultaneously couples the two upper states are studied. We consider the interplay between the squeezed field and the vacuum-induced coherence (VIC) between the two possible decay channels. The RFS for a degenerate excited doublet exhibits a high narrowing of the central line. In the situation in which the excited doublet is non-degenerate, we found that the squeezed field breaks the trapping condition attained when induced interference is maximal. A explanation of the main features in terms of dressed atomic states is given. We have also studied the probe absorption spectrum for a resonant driving field. It is shown that the probe may be amplified or absorbed over a wide range of frequencies when both quantum interference and the squeezed vacuum are considered. The sensitivity of the spectrum to the squeezed phase allows the control of the amplification/absorption of the probe signal.