Evolution of the entropy of a two-mode field interacting with a casade three-lev el atom system

Considering the larger detuning approximation and the effect of phase damping of cavity field,we have studied the time evolution of the linear entropies for the atom-field system,the field and the atom in the system of a cascade three-level atom interacting with a two-mode field.The effects of ac Stark shifts and initial states of the cavity field on all the linear entropies are analyzed.