Second-Order Correlation Function of Two-Photon Fluorescence of a Two-Level Atom in a Squeezed Vacuum.

The photon statistics of the two-photon fluorescence of a two-level atom in a squeezed vacuum is investigated by using the second-order correlation function g (2) ( t ). Based on its analytical solution, g (2) ( t ) is found to be an oscillatory function of time when the average photon number of the squeezed vacuum light field is above a threshold. The origin of the oscillatory behavior of g (2) ( t ), which generally results from the external driving field for resonance fluorescence, is the driving effect of the squeezed vacuum light field on the atom. It is also found that the oscillatory behavior of g (2) ( t ) can provide a measurement of the ac Stark effect.