Observation of Stimulated Raman Backscatter from a Performed, Underdense Plasma

Observations of stimulated Raman backscatter in an underdense hydrogen plasma are reported. The wavelength shift associated with the backscattered Raman component is consistent with a plasma with the measured electron density. The Raman backscatter is seen to decrease below detectable levels when the incident C${\mathrm{O}}_2$-laser intensity is attenuated approximately 50%, consistent with theoretical intensity thresholds of the Raman process.