Delay instabilities in light transmission of thin film with mirror

Spatio-temporal instabilities in a system formed by a thin film of two-level medium and a feedback mirror are theoretically investigated. Two mechanisms of delay instabilities connected with an interplay of the superradiance, the local field correction and the nutation oscillations are classified. The dependence of the dynamics on the ratio of the relaxation times to the delay is revealed. Influence of the delay on the threshold of spatial instability is elucidated.