Suppression Of The Stimulated Brillouin And Raman Scattering In Actively Q-Switched Fiber Lasers Through Temporal Pulse Shaping

Despite the wide range of applications and versatility, actively Q-switched fiber lasers (AQS-FLs) suffer from the multi-peak phenomenon or stepwise pulse generation under certain conditions. As such, the advantage of the stepwise tendency in AQS-FL to modify the pulse shape and create a temporal profile that minimizes the power of stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) Stokes components is taken. Accordingly a multi-objective genetic algorithm (GA) and a Monte-Carlo method is developed to solve the improved model for SBS. Additionally, the suppression of SRS is predicted and examined successfully. The proposed method is deployed for the simulation of the 5 and 10 kW peak and 10 ns wide pulses on a 4 m long, single-mode, ytterbium-doped double clad fiber under the narrow linewidth of 0.05 nm with promising suppression of SBS and SRS effects. To the best of the authors' knowledge this is the first time that such a pulse-shaping strategy is demonstrated for the SBS or SRS suppression. Furthermore reaching a 10 kW peak on single mode fibers was previously only possible via custom made fibers. Our novel method offers the possibility of optimizing and improving the utilization of different fiber types in AQS-FL systems.