Effect of Pulse Duration in Multi-Pulse Excitation of Silicon in Laser-Induced Breakdown Spectroscopy (LIBS)

Abstract

The aim of this study is to investigate the mechanisms responsible for the increase in ablated mass and signal enhancement observed on multi-pulse excitation. Several experiments were designed to obtain evidence that confirms the laser–sample and/or laser–plasma interaction, with special attention to the role of the pulse width on these effects. A train of pulses, with a separation of a few microseconds between pulses, was used for laser-induced breakdown spectroscopy (LIBS) analysis. The signal emission of Si was improved by an enhancement factor of about 60 compared to conventional single-pulse LIBS (SP-LIBS). The number of spikes, their amplitude, and their pulse duration were found to be variable for different Q-switch delays. A temporal study was performed to determine whether or not a laser–plasma interaction took place. The effect of pulse width (as responsible of laser–sample interaction) was also evaluated. The results demonstrate that, although both interactions contribute to the observed effect, the process is predominantly governed by the pulse width.