Pulse splitting of stimulated Raman backscattering with a chirped pump

Abstract

Raman amplified seed splitting was demonstrated in the backscattering scheme in a plasma, when a significant chirp was introduced into the pump. Particle-in-cell simulations have shown that a single seed laser pulse gradually splits into two, self-compressed pulses in the nonlinear amplification regime. This is in difference to previous studies of the pump chirp, which mainly have focused on its compensation for the plasma density gradient, in order to maximize the resonant amplification. The splitting, as revealed by the spectral evolution of the amplified seed, is attributed to resonance slipping, which is the result of the spatio-temporal distribution of the gain of the chirped pump.