Impact of delayed feedback of arbitrary duration in self-pulsations of a CO 2 laser

We report on a systematic investigation of the stability of a CO2 laser subjected to delayed electro-optical feedback. Such a laser roughly displays three operational intervals of stability, which we characterize using high-resolution stability charts and a video. Contrary to current belief, we find delays smaller than ∼1  μs to strongly “clean complexity,” namely, to prevent chaos and periodic pulsations with many spikes. In contrast, complex pulsations and chaos are significantly enhanced for τ>1  μs. In this range, one finds a complex alternation of periodic and chaotic phases, which are sensitive to the delay duration.