Dynamics of laser-ablation plume and ambient gas visualized by two-dimensional laser-induced fluorescence

Abstract

Summary form only given, as follows. For synthesizing new materials by laser ablation in reactive-gas atmosphere, understanding on the hydrodynamic behavior of ablation plume and ambient gas is important. In the present work, we visualized the dynamics of laser-ablation plume and ambient gas by 2DLIF. A graphite plate installed in a vacuum chamber was irradiated by Nd:YAG laser pulses at a wavelength of 1060 nm. The YAG laser beam was focused using a lens, so that the fluence of the laser pulse on the target surface was approximately 3 J/cm/sup 2/. The duration of the YAG laser pulse was 10 ns. The vacuum chamber was filled with C/sub 4/F/sub 8/ at various pressures. Tunable laser pulses having planar beam shapes were injected into the laser-ablation plume. The image of the laser-induced fluorescence was taken using a charge-coupled device with a gated image intensifier. We visualized the density distribution of C/sub 2/, which was a typical species ejected from the graphite target. To visualize, the dynamics of ambient gas, we decomposed C/sub 4/F/sub 8/ partly to produce CF/sub 2/ radicals. A compact plasma source was used for the decomposition of C/sub 4/F/sub 8./ The density distribution of CF/sub 2/ was visualized by 2DLIF. We observed a compressed layer in the density distribution of CF/sub 2/, which was due to a shock wave excited by the expansion of the plume. The expansion dynamics of the plume and the shock front was explained well by a conventional theory.