Experimental study on buildup dynamics of a harmonic mode-locking soliton fiber laser

In this paper, we experimentally investigate the onset dynamics of harmonic mode-locking (HML) in a short-cavity all-polarization-maintaining fiber laser using time-stretch spectroscopy. We observe a transient multi-pulse state evolving into a stable HML state. Moreover, a bunch of metastable short-lived mode-locking states are recorded before the laser entered the HML state. In these transient states, sudden changes including the formation and destruction of single broadband pulses are observed.