Generation of a two-mode squeezed vacuum field in forward four-wave-mixing process in an ensemble of Λ atoms

We develop the theory to describe the generation of entangled-photon pairs in the parametrically induced transparency regime in an ensemble of Λ atoms. A highly effective conversion of the monochromatic drive field into entangled-photon pairs is predicted. In the suggested regime, the generation of entangled photons has some advantages as compared to the well-known methods, such as a narrow frequency band and a low threshold for the drive power. The two-mode squeezed vacuum generation is thorouhly investigated.