Intensity saturation of stimulated Raman scattering by ion-wave coupling

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Abstract
Nonlinear saturation of stimulated Raman scattering caused by ion‐wave coupling is investigated analytically and numerically. Various linear damping conditions for plasmons and ion‐acoustic waves are included in the analysis. The main results can be summarized in terms of the normalized damping coefficient β (β=Raman gain length/plasmon absorption length), which decreases with the laser intensity I as β∼I−1/2. At low intensities (β>4) the Raman reflectivity increases according to the well‐known three‐wave process. At high intensities (0.2<β<2) a steady state still exists and the reflectivity is saturated as a function of the laser intensity. At very high intensities (β<0.1) temporally spiky and chaotic reflectivity is obtained. The reflectivities remain at very low levels, except for large interaction lengths.