Boosting the performance of Brillouin amplification at sub-quarter-critical densities via reduction of parasitic Raman scattering

Abstract

Raman and Brillouin amplification of laser pulses in plasma have been shown to produce picosecond pulses of petawatt power. In previous tudies, filamentation of the probe pulse has been identified as the biggest threat to the amplification process, especially for Brillouin amplification, which employs the highest plasma densities. Therefore it has been proposed to perform Brillouin scattering at densities below n cr /4 to reduce the influence of filamentation. However, parastic Raman scattering can become a problem at such densities, contrary to densities above n cr /4, where it is suppressed. In this paper, we investigate the influence of parasitic Raman scattering on Brillouin amplification at densities below n cr /4. We expose the specific problems posed by both Raman backward and forward scattering, and how both types of scattering can be mitigated, leading to an increased performance of the Brillouin amplification process.

Joule-Level High-Efficiency Energy Transfer to Subpicosecond Laser Pulses by a Plasma-Based Amplifier

“…Without reducing the scSBS gain, the beam losses from spontaneous Raman scattering and collisional damping might be limited with the use of a plasma with a density ramp and a much higher temperature. An initially shorter seed pulse will also reduce these losses, and would be better adjusted to the self-similar regime, increasing the pulse compression [18,26,34]. Much larger energy transfers might be reached using longer pump and plasma, larger focal spots of homogeneous and hyper-Gaussian profiles.…”