A robust plasma-based laser amplifier via stimulated Brillouin scattering

Brillouin amplification in plasma is more resilient to fluctuations in the laser and plasma param- eters than Raman amplification, making it an attractive alternative to Raman amplification. In this work, we focus on high plasma densities, n₀ > n_cr/4, where stimulated Raman scattering is not possible and laser beam filamentation is the dominant competing process. Through analytic theory and multi-dimensional particle-in-cell simulations, we identify a parameter regime for which Brillouin amplification can be efficient while maintaining filamentation of the probe at a controlled level. We demonstrate pump-to-probe compression ratios of up to 72 and peak amplified probe fluences over 1 kJ/cm² with ≃ 50% efficiency. High pulse quality is maintained through control of parasitic filamentation, enabling operation at large beam diameters. Provided the pump and probe pulse diameters can be increased to 1 mm, our results suggest that Brillouin amplification can be used to produce sub-picosecond pulses of petawatt power.