Brillouin Backscattering and Parametric Double Resonance in Laser-Produced Plasma

Brillouin backscattering from laser-produced plasmas of hydrogen and deuterium has shown an isotope effect in the red-side region of the generated second-harmonic light. This isotope shift is explained by the parametric instability at the cutoff region using the phase-matching condition of the waves. The decrease of the reflectivity appeared when the laser intensity increased up to 1 order of magnitude larger than the threshold of the parametric instability. A broad-band laser showed more effective heating of the plasma than a narrow-band laser.