On the Q-switching bunch dynamics in the build-up of stretched-pulse mode-locking

In this paper, we experimentally investigate a rich set of Q-switching bunches in the build-up of stretched-pulse mode-locking of an erbium-doped fiber laser. Interestingly, regular clustering of periodic Q-switched mode-locking states is observed in the self-starting process. Moreover, with time-stretch spectroscopy, we record periodic pulse-to-pulse spectral evolution occurring in these turbulent and rapidly-evolving pre-mode-locking states.