Abstract
An excitable semiconductor micropillar laser with delayed optical feedback is able to regenerate pulses by the excitable response of the laser. It has been shown that almost any pulse sequence can, in principle, be excited and regenerated by this system over short periods of time. We show experimentally and numerically that this is not true anymore in the long term: rather, the system settles down to a stable periodic orbit with equalized timing between pulses. Several such attracting periodic regimes with different numbers of equalized pulse timing may coexist and we study how they can be accessed with single external optical pulses of sufficient strength that need to be timed appropriately. Since the observed timing equalization and switching characteristics are generated by excitability in combination with delayed feedback, our results will be of relevance beyond the particular case of photonics, especially in neuroscience.
Highlights
Excitability is observed in many natural and artificial systems, including spiking neurons, cardiac cells, and semiconductor lasers
Since the long-term information is encoded in the number of pulses in the feedback loop, we investigate how one can switch between different equalized stable pulse trains
We have shown how any initial pulsing pattern equalizes to an equidistant pulse train in the excitable micropillar laser with delayed optical feedback
Summary
Excitability is observed in many natural and artificial systems, including spiking neurons, cardiac cells, and semiconductor lasers. When subject to delayed feedback, an excitable system can either remain in its quiet state for small external perturbations or, with an adequate control pulse of sufficient strength, it can regenerate its own excitable response after the reinjection time τ This very general mechanism for self-pulsations has been implemented in different optical systems, including a coherently driven vertical-cavity surface-emitting laser (VCSEL) [2], a VCSEL subject to optoelectronic feedback [3], coupled semiconductor lasers [4], a photonic resonator with optical self-feedback [5], and a micropillar laser with integrated saturable absorber [6]. In the presence of delayed optical feedback, it sustains trains of regenerative optical pulses, which can be asymmetrically perturbed by noise [6] or added and erased by single optical perturbations [11]
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