Atomic emission spectra and field non-classical properties

This paper studies the interaction of a $\Lambda$-type three-level atom with a single mode field. It discusses the emission spectrum characteristics of the $\Lambda $-type three-level atom driven by the photon-added coherent field. By means of the second-order degree of coherence, it shows some nonclassical properties of the cavity field, such as sub-Poissonian photon-number distribution and the two-time intensity--intensity correlation which violates the Cauchy--Schwarz inequality.