Nonlinear evolution of stimulated Raman scattering near the quarter-critical density

Abstract

Nonlinear evolution of stimulated Raman scattering (SRS) near the quarter-critical density is studied using one-dimensional (1D) and two-dimensional (2D) particle-in-cell simulations in homogeneous plasmas. In 1D configuration, with two-plasmon decay (TPD) instability excluded, the system evolves into two regimes distinguished by whether density cavities have been formed or not. At low temperatures, a cavity regime characterised by high absorption and low reflection, and at high temperatures nonlinear frequency shift regime due to particle trapping, are observed. Furthermore, a competition between SRS and TPD in 2D simulations reveals that the nonlinear SRS does play a significant role near the quarter-critical density, whose influences were mostly neglected before.