Experimental investigations of plasma-wave excitation and harmonic generation in a plasma produced by a high-power laser pulse

Interactions mechanisms between 1.06-micron Nd laser radiation and high-temperature plasmas produced from different targets are studied experimentally at light flux densities ranging from 10 to the 12th power to 4 by 10 to the 14th power W/sq cm. An intercomparison of measurements made by various techniques indicates that the effective absorption of laser radiation is caused by the development of t to p+S and t to p+p decay instabilities. It is shown that plasma radiation at a frequency equal to 3/2 the lasing frequency results from Raman scattering by plasma waves with a frequency close to 1/2 the lasing frequency. Experimental threshold light flux densities obtained from aluminum, lead, lithium deuteride, polyethylene, and deuterated polyethylene targets are found to be in good agreement with theoretical predictions.