Two-level atom in a squeezed vacuum with the two photon process via ac-Stark effect

In this article we introduce analytical formulas for the probe absorption spectrum and the second correlation function for a two-level atom driven by the non-degenerate two-photon and damped by a broadband multi-mode squeezed vacuum. We find that in two-photon process the squeezed vacuum has a driving effect on the atom which can lead to an ac Stark effect for a critical value of the average photon number, We see that the value of bandwidth squeezed vacuum play some role in absorption, amplification and electromagnetic transparence of probe field.