Multiwavelength laser solid--target Interaction at 10 microns

Some aspects of multiple-wavelength interaction on solid targets have been experimentally studied at CO2-laser wavelengths with 1-nsec pulses. Contrary to predictions, the use of a two-line (10.6- and 9.6-μm) source does not reduce the back reflection. This result could be explained by a very short Brillouin interaction length or/and a very low saturation level. The hot-electron production is also not significantly modified by multiline illumination. A signal at the frequency sum indicates that, even at Ilambda2 as low as 5 x 1013 W cm-2 μm2, the critical surface is not well defined and that both the 9.6- and 10.6-μm light interact in the same resonant zone. Finally, significant sidebands were measured at 8.7 and 12 μm. Some 1 (1)/(2) -dimensional simulations with mobile ions indicate that those sidebands probably originate from the beat frequency resonant density at 0.0123n/sub c/