“…This model has been broadly used in order to study the time evolution of the atomic and photon operators, the second order coherence function, the one and two-mode squeezing, the atomic-dipole squeezing and the emission spectra [11,[13][14][15][16][17][18]. Usually, the two-level system has been considered initially in the excited state and the two-photons have been chosen initially in two independent coherent states [11,15,16,18], two mode squeezed states [11], pair-coherent states [13], correlated SU(1,1) coherent states [14], etc. The Λ configuration, also called the Raman coupled model, when the intermediate level can be adiabatically eliminated was studied by Abdalla, Ahmed and Obada [19], and independently by Gerry and Eberly [20].…”