Observation of the nonlinear saturation of Langmuir waves driven by ponderomotive force in a large scale plasma

We report the observation of nonlinear saturation of Langmuir waves produce d by a probe laser beam interacting with a high intensity pumping laser bea m. Amplification of the probe beam is observed and interpreted as scatterin g of pump energy by a Langmuir wave that is produced by the beating of the two beams. It is found that, as the probe beam amplitude is increased, the scattering and Langmuir wave amplitude do not increase proportionally, demo nstrating that the wave is nonlinearly saturated consistent with saturation by secondary-ion-wave instabilities.