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.
Summary form only given. We suggest a promising way to obtain the squeezing of vacuum fluctuations. We study the interaction of linearly polarized light with atoms in a double-/spl Lambda/ configuration, where the two lower levels are Zeeman sublevels of the atomic ground state and the upper levels are the hyperfine components of the atomic excited state. In such systems, Kerr nonlinearity associated with the ac-Stark effect causes self-rotation of the elliptical polarization. At the same time when the linearly polarized light traverses such a medium, a squeezed vacuum is produced in the orthogonal polarization.
We study the interaction of a two-level atom with two lasers of different frequencies and amplitudes: a strong laser of Rabi frequency $2{\ensuremath{\Omega}}_{1}$ on resonance with the atomic transition, and a weaker laser detuned by subharmonics $(2{\ensuremath{\Omega}}_{1}/n)$ of the Rabi frequency of the first. We find that under these conditions the second laser couples the dressed states created by the first in an
n-photon process, resulting in ``doubly dressed'' states and in a ``multiphoton ac Stark'' effect. We calculate the eigenstates of the doubly dressed atom and their energies, and illustrate the role of this multiphoton ac Stark effect in its fluorescence, absorption, and Autler-Townes spectra.