Experimental investigation of stimulated Raman and Brillouin scattering instabilities driven by two successive collinear picosecond laser pulses

摘要

Backward stimulated Raman and Brillouin scattering (SRS and SBS) are experimentally investigated by using two successive 1-mu m, 1.5-ps FWHM laser pulses. The collinear pulses, separated by 3 or 6 ps and of moderate laser intensities (similar to 2 x 10(16) Wcm(-2)), are fired into a preionized He plasma of density similar to 2.5 - 6 x 10(19) cm(-3). The electron plasma waves and ion acoustic waves, respectively driven by SRS and SBS, are analyzed through space-and time-resolved Thomson scattering. Depending on the laser and plasma parameters, we observe the effect of the first pulse on the time-resolved SRS and SBS signals of the second pulse. The measurements are found to qualitatively agree with the results of a large-scale particle-in-cell simulation.