Starting a Figure-9 laser using the "roaming mode"

Self-starting performance, which is typically related to the likelihood of a laser going promptly into mode-locking status as pump power ramps up, has always been an important factor while evaluating a Figure-9 laser. Here, quite strikingly, we find that the conventional way to assess self-starting characteristics may not fully reflect the laser's starting capability. Specifically, we perform a "roaming mode", where the mode-locking status is accessed by continuously rotating the waveplates after the pump power is fixed. Compared with conventional way, the roaming mode is seen to yield significantly more mode-locking states. In roaming mode, scanning from different directions produce qualitatively the same results. Our findings suggest there are indirect but accessible mode-locking states in the parameter space. The rotating action in "roaming mode" is believed to provide the necessary physical excitation to enable these states. Our findings provide an updated guideline for designing and optimizing Figure-9 lasers.