Atoms in a narrow-bandwidth squeezed vacuum

Two possible descriptions of evolution of a two-level atom driven by a stro ng laser field and subjected to a squeezed vacuum with finite bandwidth are discussed. One is the master equation approach in which the squeezed vacuu m is treated as a Markovian reservoir to the atom, and the other is the cou pled-systems (or cascaded-systems) approach in which the degenerate paramet ric oscillator (DPO) producing squeezed vacuum is a part of the system. Exa mples of optical spectra obtained using both approaches are given.