Particle-in-Cell Simulations of Laser Amplification via Stimulated Raman Backscattering

Raman amplification in plasma (RA) offers a promising route for generating ultra-intense, ultra-short laser pulses beyond the limits of conventional solid-state laser systems. In this process, a long pump laser interacts with a counter-propagating short seed pulse within an underdense plasma, mediating energy transfer via stimulated Raman backscattering. The plasma acts as a nonlinear optical medium that enables efficient longitudinal energy transfer over millimeter-scale distances without optical damage thresholds, allowing for relativistic intensities. Key physical processes governing the efficiency and stability of RA include pump depletion, nonlinear wave coupling, wave breaking, and kinetic effects. Recent experimental and computational advances have demonstrated amplification factors >30x, energies transfer to the seed >200 mJ, and efficiencies >10%. We report on current experimental plasma-based amplifier results and our understanding of them through hydrodynamic and PIC simulations, along with computational studies of the effects limiting efficient amplification such as angular, translational, and temporal beam alignment.