Laser-Induced Breakdown Spectroscopy for Microanalysis

Abstract Laser induced breakdown spectroscopy is a fast non-contact technique for the analysis of the elemental composition of any sample. Our focus is to advance this technique into a new regime where we use pulse energies below 100 μJ. This regime is referred to as microLIBS or μLIBS. Preliminary pulse emission scaling of Na in latent fingerprints has been investigated for ∼ 130 fs, 266 nm pulses with energies below 15 μJ. The single shot limit of detection is expected to be approximately 3.5 μJ for this case. A 2D map of a fingerprint on a Si wafer has been successfully acquired using 5 μJ pulses. The detection sensitivity of micro-laser-induced breakdown spectroscopy (μLIBS) is improved by coupling it with a resonant dual-pulse method called laser ablation-laser induced fluorescence (LA-LIF). This technique was investigated using a waterjet sample containing a low concentration of Pb by weight as an analyte which was ablated by a 266 nm, frequencyquadrupled Q-switched Nd:YAG laser at an energy of ∼ 170 μJ. After a short delay the resulting plume was re-excited with a nanosecond laser pulse tuned to a specific transition for the element of interest. In the case of the resonant dual-pulse LIBS the limit of detection was found to be 73 ppb for Pb in water. This result is promising and could be implemented with fiber or microchip lasers with multi-kHz repetition rates as excitation sources for a portable μLIBS water monitoring system or a fingerprint scanner.