Study of stimulated Raman and Brillouin scattering in a finite interaction region under the convective instability condition

We discuss stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS) under the convective instability condition with a one-dimensional three-wave interaction (3WI) model. Using linear theory, we deduce the temporal growth rate, gain exponent, and reflectivity of the backward scattered wave in a finite interaction region. We find that the growth rate is not only determined by the laser intensity and plasma density and temperature, but also related to the spatial gain. The length of the interaction region is important to the gain exponent and backscattering level. We simulate the developments and evolutions of SRS and SBS based on the 3WI equations. Our numerical results consist with the linear theory.