Eliminating stimulated Raman backscatter through induced laser bandwidth concomitant from forward scatter

Stimulated Raman Scattering (SRS) is a fundamental process within the nonlinear optics of plasmas. In SRS an incoming light wave scatters into a backward or forward light wave and a forward going plasma wave. Understanding and controlling SRS backscatter it is important for applications such as Inertial Fusion Energy (IFE) and Raman Amplification. SRS backscatter can limit the gain for indirect drive IFE by degrading drive symmetry and generating preheat. We show through OSIRIS simulations and envelope equations that SRS backscatter can in some cases be eliminated by the induced bandwidth from Stokes and anti-Stokes generation from the incident laser light scattering off the forward scatter generated (fast) plasmas wave (this can also be viewed as photon acceleration within a single wavelength of the fast wave. If the loss of pump energy occurs faster than SRS backscatter growth the backscatter can be prevented. We present examples where the fast wave is excited by an external driver and find the threshold value for the fast wave amplitude that eliminates backscatter. Preliminary results on the effects of ion motion and finite width lasers will also be presented.