Hysteresis of a passively mode-locked fiber laser: effects from cavity dispersion.

Hysteresis is a common phenomenon in passively mode-locked lasers and refers to the effect where the thresholds marking transitions between different pulsation states are not the same for an increasing or decreasing pump power. Despite wide presence in experimental observations, the general dynamics of hysteresis remains elusive, largely due to the challenge to acquire the full hysteresis dynamics of a given mode-locked laser. In this Letter, we overcome this technical bottleneck by fully characterizing an exemplar figure-9 fiber laser cavity, which exhibits well-defined mode-locking patterns in its parameter space or "primitive cell." We varied the net cavity dispersion and observed the salient change of hysteresis characteristics. Specifically, transiting from an anomalous to a normal cavity dispersion is found to consistently increase the likelihood of the single-pulse mode-locking regime. To the best of our knowledge, this is the first time that a laser's hysteresis dynamic is fully probed and related to fundamental cavity parameters.