Time-stretch probing of ultra-fast soliton dynamics related to Q-switched instabilities in mode-locked fiber laser.

Ultra-fast soliton dynamics is one of the most attractive phenomena in the mode-locked fiber laser. However, the formation and breakup of solitons are difficult to observe, due to the transient nature of the process. Using the time-stretch technique, we are able to trace the real-time evolution of the soliton bound state formation and mode-locking build-up. Q-switched instabilities exist in both booting processes. Moreover, we find that the evolving patterns of soliton bound states are highly dependent on their initial conditions. Here, two types of soliton pairs are observed in the cavity and their typical forming dynamics are recorded and analyzed. Our findings uncover a diverse set of soliton dynamics in a mode-locked fiber laser and thus promote our understandings about complex dynamics in nonlinear optical systems. These results also provide a valuable reference for further theoretical studies.