Observation of steepening in electron plasma waves driven by stimulated Raman backscattering

Harmonics of plasma waves excited by ${\mathrm{CO}}_2$-laser–induced stimulated Raman scattering have been observed by frequency- and wave-number-resolved ruby Thomson scattering. Measurements of their relative amplitudes agreed with predictions of nonlinear warm-plasma wave-steepening theory up to the maximum observed amplitude of the fundamental component, n${̃}_1$/$n_0$=16%.