Intensity–intensity correlations in a V-type atom driven by a coherent field in a broadband squeezed vacuum

摘要

We study the intensity–intensity correlation in a closely spaced doublet V-type three-level atom driven by an external coherent field and damped by a broadband squeezed vacuum. We are interested in the manner in which the atom emits photons under the combined effect of quantum interference and squeezed vacuum. For distinguishable photons and degenerate transitions, the squeezed field produces anticorrelation, whereas for nondegenerate transitions the effect of the squeezed field is the surpassing of the antibunching during certain time intervals. We find that bunching/antibunching behaviour and the symmetry of the two emission processes can be controlled by the relative phase of the squeezed vacuum to the coherent field. For particular conditions we show a bunching behaviour which turns to antibunching when the two-photon correlations in the squeezed vacuum are reduced to the classical level. Therefore, this transition must be attributed to the quantum nature of the squeezed vacuum. We also study the sideband correlations. We find that squeezed vacuum makes the sidebands evolve at different rates which are phase dependent.