Noise-induced escape through a chaotic saddle: lowering of the activation energy

The noise-induced escape mechanism is investigated for a prototype time-discrete nonequilibrium system describing a laser in a ring cavity with optical feedback, the Ikeda map. For certain parameter values a chaotic saddle is embedded in the basin of attraction of the metastable state. This results in a lowering of the escape threshold for the activation energy, which is established by employing the theory of quasipotentials. Our findings are explained by the computation of the most probable exit path (MPEP), which lies partly on the chaotic saddle. The enhancement of escape turns out to be maximal if the MPEP lies entirely on the chaotic saddle.