Abstract
We investigate the evolution of the atomic quantum entropy and the atom-field entanglement in a system of an Xi-configuration three-level atom interacting with a two-mode field with additional forms of nonlinearities of both the field and the intensity-dependent atom-field coupling. With the derivation of the unitary operator within the frame of the dressed state and the exact results for the state of the system we perform a careful investigation of the temporal evolution of the entropy. A factorization of the initial density operator will be assumed, considering the field to be initially in a two-mode pair coherent state. The effects of the mean photon number, detuning, Kerr-like medium and the intensity-dependent coupling functional on the entropy will be analyzed.