Active Q-Switching in Fiber Laser Circuits

By the example of a fiber laser based on bismuth active centers, the influence of the structural scheme of the laser on the efficiency of a regime with periodic active Q-switching is demonstrated. Numerical simulation of various circuits allows us to understand the details of the formation of the multi-peak struc-ture of the output signal and, in many cases, to increase the efficiency of Q-switching, keeping at the output a single pulse that saturates the active medium as deeply as possible. For this purpose, a method of Q-switching is proposed, based on a short-term repeated increase in Q-factor in each period. Calcula-tions have shown that this method allows one to obtain single pulses with a duration of about 0.01 times the time of a single pass through the cavity.