Laser-induced emission spectra of stainless steels and aluminum irradiated with nanopulse lasers without setting delay: potential applications to remote sensing and laser micromachining

Spectral lines from the impurities held in stainless steel and in aluminum can be clearly identified in the UV and the visible spectra when emission is laser induced. These spectroscopic lines can be initiated in metal irradiated at moderate laser optical densities of about 2.5×108W/cm2. In addition to the lines arising from impurities found in some metals, it was found that some spectroscopic lines from iron oxide formed during irradiation were also detected at the above-mentioned power density. It was found that lines observed from iron oxide are consistent with what is reported in the literature. The investigations reported were produced on samples at optical densities that are sufficient to create an electric field that is about 10 times the air electrical breakdown near the focal point. The results reported were obtained without setting any delay between the laser Q-switch and the data acquisition. The spectroscopic data are comparable to those shown in the literature by laser-induced breakdown spectroscopy in term of signal-to-noise ratio and are promising in detecting impurities such as heavy metals in remote sensing applications, where pulse delay is not always practical due to atmospheric conditions and power requirements. As a marking procedure is used during the investigations, the method demonstrates how spectroscopic monitoring in real time can be applied during a procedure in laser micromachining applications.