The temporal evolution of entanglement for a single-mode field interacting with a two-level
atom via intensity-dependent coupling in the off-resonant case has been studied, where the
leakage of photon through the cavity is taken into account. The effects of cavity damping on
the coherence properties of the atom and the field are studied. The amount of entanglement is
compared with the total correlations. It is found that the atom–field system is inhibited from
going into a pure state in the off-resonant case.