Scattered and absorption spectra of a system of atoms under squeezed vacuum excitation

Abstract

We study the scattered and absorption spectra of two identical two-level atoms interacting with a squeezed-vacuum field. The results are compared with those obtained for the atoms interacting with a thermal field. We show that in the thermal field the emitted spectrum consists of two peaks, located at frequencies ±Ω 12, where Ω 12 is the dipole-dipole interaction between the atoms. When the thermal field is replaced by the squeezed-vacuum field the spectrum shows one peak located at the frequency -Ω 12. These changes in the spectrum are due to the selective population of collective atomic states in the squeezed vacuum. We also calculate the absorption spectrum of a weak prove field by a two-atom system. We show that in the thermal field the absorption spectrum consists of two absorption-like peaks, located at ±Ω 12, indicating an attenuation of the probe beam by the atomic system. In the squeezed-vacuum field, however, the adsorption spectrum exhibits negative values at the frequency -Ω 12, indicating that stimulated emission takes place, amplifying the probe beam at the expense of the squeezed-vacuum field. These results suggest new ways of examining and detecting pure states and population inversion produced by the squeezed light.