Ultra-low-energy and high-speed micro-laser-induced breakdown spectroscopy using GHz repetition rate pulses

Using GHz repetition rate pulses in burst mode has demonstrated numerous advantages for highly efficient material removal. In this work, we present high-speed (over 100 kHz) micro-laser-induced breakdown spectroscopy (micro-LIBS) with ultra-low pulse energies in the range of 10-200 nJ using our recently developed 2.8 GHz burst-mode Yb-doped fiber laser. We delivered 40 ps-long pulses to the sample with a beam diameter of about 18 microns. A systematic LIBS study was conducted on stainless steel (SS) at different burst durations and burst energies to study their effects on the optical emission spectrum. Finally, the electron temperature and electron density were determined using the Boltzmann plot method and Stark-broadened line profile analysis, respectively.