Q-switching instability in a mode-locked semiconductor laser

We suggest semianalytic estimates for the Q-switching instability boundary of the continuous-wave (cw) mode-locking regime domain for a ring-cavity semiconductor laser. We use a differential delay laser model that allows us to assume large gain and loss in the cavity, which is a typical situation for this class of lasers. The Q-switching instability boundary is obtained as a Neimark-Sacker bifurcation curve of a map describing the transformation of pulse parameters after a round trip in the cavity We study the dependence of this boundary on laser parameters and show that our theoretical results are in qualitative agreement with the experimental data obtained with a passively mode-locked monolithic semiconductor laser.