Multiple laser parametric study of fiber-laser-induced breakdown spectroscopy

An integrated investigation of pulse energy (0-0.8 mJ), pulse width (2-500 ns), and repetition rate (1 Hz-4 MHz) was carried out on laser-induced breakdown spectrometry (LIBS). An increase in pulse energy led to a significant signal elevation, yet its speed slowed down at a longer pulse width, which helps to lessen the electron density and ablation threshold. The repetition rate showed greater impact at higher pulse energy, and a threshold of about 200 Hz was observed for signal enhancement, exceeding which the ablation threshold of aluminum decreases logarithmically in the case of a 250 ns pulse width. Up to 29.0% of the sensitivity enhancement and 43.9% of the limit of detection (LOD) improvement were obtained under a high laser repetition rate of 20 kHz, resulting in an agreeable LOD of down to several tens of ppm considering the low laser irradiance applied here. In summary, to achieve better quantification results, higher pulse energy, moderate pulse width, and higher repetition rate should be applied.