Mitigation of Stimulated Brillouin Scattering (SBS) for power scaling of narrow linewidth fiber amplifiers
High power pulsed lasers emitting peak power levels in the order of PetaWatts (10^15 Watts) are of much interest for several applications since they have significant advantages of scale and cost. For instance, the ICAN project, in which Prof Johan Nilsson (International PI) is one of the investigators envisages the realization of PW sources through coherent beam combining of multiple chirped pulse amplified (CPA) fiber amplifiers for futuristic applications such as particle colliders. Other applications such as the Starshot project requires coherent beam combination of continuous-wave light. For efficient beam combining, all the amplifiers need to be highly coherent. One of the key limitations in scaling the output power of the individual rare-earth doped amplifiers is Stimulated Brillouin Scattering (SBS).
The onset of the SBS process in the optical fiber amplifiers may be controlled by chirping the master oscillator linewidth through appropriate phase modulation. One of the most promising approaches for such phase modulation is the optimized modulation waveform obtained through nonlinear multi-parameter Pareto optimization using a temporal-amplitude-domain finite-difference Brillouin solver with noise initiation. In the proposed work, we intend to build a model to describe the SBS dynamics in a narrow linewidth fiber amplifier. Using this model, we plan to identify phase modulation waveforms optimized to mitigate SBS through Pareto optimization. Finally, we will validate the above model through controlled experiments leading to the demonstration of power scaling in a narrow linewidth fiber amplifier.