Abstract

We consider dressed-state population trapping in the system of a two-level atom interacting with a squeezed vacuum. This topic has been discussed previously by Courty and Reynaud [1] within the confines of the secular approximation. In the present treatment, although we employ a dressed atom approach, it is essential not to make the secular approximation: the effects of principal interest dissappear when the secular approximation is employed. We show that the dressed state population shows a global maximum for a particular value Φ = –Φ₀ of the phase difference Φ between the driving field phase and the squeezed vacuum phase. There is, however, no corresponding global minimum at Φ = –Φ₀. This asymmetry dissappears when the secular approximation is made. In addition, there is a local maxima and a local minimum at Φ = ±π. For Φ = –Φ₀, practically complete population trapping can occur. This results in the complete disappearance of two of the three peaks of the resonance fluorescence spectrum. We have verified that this is a purely quantum effect of the squeezed vacuum. That is, if we replace the squeezed vacuum by a field which has the maximum degree of two-photon correlations permitted for a field with a classical analogue, the normal three-peaked resonance fluorescence spectrum is obtained. Thus the observation of this population trapping would be a striking confirmation of the essentially quantum nature of the squeezed vacuum.

© 1998 IEEE