Study on application of laser spectroscopic techniques to laser processing

Miyabe, Masabumi   

We have studied the applicability of spectroscopic technique for obtaining process information needed for laser decommissioning and other various laser processing techniques. When a material is irradiated with intense laser pulses, atomic species eject from the surface which absorbing the light energy via inverse Bremsstrahlung process and laser plasma grows rapidly. Thus various properties of the generated laser plasma strongly depend on the duration of the laser irradiation. Although previous studies have reported differences in emission characteristics between Nd:YAG lasers with about 10 ns-pulse and long-pulse lasers with about 100 ns-pulse, little is known about the emission and/or absorption characteristics of the plasma produced through the irradiation of longer than 10 ms duration, which is common in current laser processing. In this study, we investigated the emission characteristics of the laser plasma produced in atmospheric air using a QCW (Quasi Continuous Wave) fiber laser. As a result, it was found that the emission intensity of oxide molecules is enhanced. Also, only for zirconia and gadolinia targets, strong emission lines of atomic species were observed. From the images recorded during laser ablation process, it was observed that the sputtered materials were burned while floating in the air and this might contribute to strong emission signal of atomic species. This study demonstrated the possibility of applying emission spectroscopy to laser processing to evaluate elemental composition of the processed materials.