  Atomic collisions are included in an interacting system of optical fields and
trapped atoms allowing field amplification. We study the effects of collisions
on the system stability. Also a study of the degree of entanglement between
atomic and optical fields is made. We found that, for an atomic field initially
in a vacuum state and optical field in a coherent state, the degree of
entanglement does not depend on the optical field intensity or phase. We show
that in conditions of exponential instability the system presents at long times
two distinct stationary degree of entanglement with collisions affecting only
one of them.
