Exploring the Saturation Levels of Stimulated Raman Scattering in the Absolute Regime

This Letter reports new experimental results that evidence the transition between the absolute and convective growth of stimulated Raman scattering (SRS). Significant reflectivities were observed only when the instability grows in the absolute regime. In this case, saturation processes efficiently limit the SRS reflectivity that is shown to scale linearly with the laser intensity, and the electron density and temperature. Such a scaling agrees with the one established by T. Kolber et al. [Phys. Fluids B 5, 138 (1993)] and B Bezzerides et al. [Phys. Rev. Lett. 70, 2569 (1993)], from numerical simulations where the Raman saturation is due to the coupling of electron plasma waves with ion waves dynamics.