Suppression of Q-switch instabilities by feedback control in passively mode-locked lasers.

We propose a feedback technique for obtaining stable mode-locked operation in lasers that would normally exhibit Q switching. Using the Haus model with population dynamics, we examine numerically the case in which the intensity is monitored by a slow detector and fed back to the pump power after electronic derivation. This approach allows elimination of Q switching in all situations considered, in particular, in lasers with a long upper-state lifetime.