  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.
