Dynamics and spectroscopy of the laser plume and generation of nanoparticles

The dynamics and the spectral kinetic characteristics of the plume emerging in the vicinity of graphite targets, pressed pellets consisting of zirconium oxide powder stabilized with yttrium (YSZ) and of garnet stock with neodymium (YAG:Nd) are studied. The targets are irradiated in air at room temperature using a repetitively pulsed CO2 laser with a wavelength of 10.6mm, a peak power of up to 9 kW, a pulse energy of up to 1.69 J, and a pulse duration of 330ms at a level of 0.1. The plume propagates normally to the target surface at an angle of 45° relative to the laser radiation. The spectral kinetic characteristics of the plume luminescence are discretely measured along the entire length. It is demonstrated that the plumes of all targets represent the "ows of a weakly nonequilibrium gas plasma with a temperature of 10 kK (graphite) and 3.1...4.7 kK (YSZ and YAG:Nd pressed pellets). The plume size is determined by the peak power of the laser pulse. The luminescence of the two-atom radicals (C2 in graphite; ZrO and YO in YSZ; and YO, AlO, and NdO in YAO:Nd) dominates in all of the plumes. A relatively high temperature of the graphite plume is maintained owing to the energy of the exothermic reaction involving the association of carbon atoms and the energy of the vibrationally excited molecules resulting from this reaction. The dynamics of plasma plume was studied by luminescence imaging and shadowgraphy.© (2007) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.