Theoretical and experimental study on nonlinear effects of mode-locked and extracavity modulation nanosecond pulsed laser

Through simulation calculations and experiments, the two popular methods of generating nanosecond (ns) pulsed laser were studied respectively. A new method for generating a ns pulsed laser with high power and ultra-high repetition frequency by using dispersive fiber after SESAM mode-locked oscillator was proposed. In the simulation calculation of the mode-locked ns pulsed laser, the time-frequency evolution characteristics of the laser formation process were analyzed. The variation process of the stimulated Raman scattering (SRS) effect was obtained at different injection powers. In the simulation calculation of the extracavity modulation ns pulsed laser, the threshold of the stimulated Brillouin scattering (SBS) effect was obtained in the 4-stage fiber amplification experiment. Then, the nonlinear dynamics model of the ns pulsed fiber laser was established by considering various nonlinear effects. The results showed the theoretical models were consistent with the experimental investigations. This provided a new way to further optimize the parameter of ns pulsed fiber lasers and also contribute to solve nonlinear damage problems in such lasers.