| Laser-induced breakdown spectroscopy (LIBS) is an analytical technique that has been given significant attention as a method for fast elemental analysis. Even though LIBS has many advantages over other analytical methods, size requirements have limited most applications to laboratory analysis.;This project was set forth to investigate the possibility of employing all-solid-state diode-pumped miniature (microchip) lasers as sources of light for LIBS and to estimate the analytical performance of LIBS based on these systems.;The study began with the diagnostics of the microchip laser-induced plasma. Plasma parameters such as size, temperature, electron number density and temporal behavior of the emission were studied using both traditional spectroscopy and CCD photography. The small plasma size (100 mum above target surface) and short lifetime (1.5-2 ns) did not allow detailed spatial and temporal study of plasma by conventional means. However, a pump-probe method based on an optical delay setup provided information about the absorption properties of the plasma on the sub-nanosecond time scale. Maximum absorption was measured 1.2 ns after the laser pulse while the plasma became almost transparent after 4 ns.;The effect of both target properties and laser parameters on the ablation properties of the microchip laser was studied. Microchip lasers produce well-defined craters, which allow easy estimation of the mass removed per laser shot. The high spatial and depth resolution of the microchip laser ablation was employed in applications such as depth profiling and trace element analysis. Detection limits for Cr, Si, Ni, and Mo in steel alloys were 100 ppm or lower, but were a hundred times higher in powdered substrates.;The microchip laser was employed in the detection of aerosols by LIBS. Laser-induced plasma was formed on particles which passed through the focal volume of a tightly focused laser during the laser pulse. The efficiency of detecting particles of various particle types and sizes was investigated as well as the use of the plasma emission for the identification of these particles. The results show the potential usefulness of microchip laser LIBS for the real-time detection and identification of particles in air. Potential applications of such a capability include real-time assessment of industrial atmospheres, clean room monitoring and bio-safety. |
