Micro-laser-induced breakdown spectroscopy using GHz repetition rate pulses at nJ pulse energy

Abstract Using GHz repetition rate pulses in burst mode has shown significant attention, particularly in laser micromachining, due to its ability to enable highly efficient, low-energy material removal. In this work, we introduce the first Laser-Induced Breakdown Spectroscopy (LIBS) in the ablation-cooled regime. By employing GHz repetition rate pulses, we present a high-speed (100 kHz) micro-LIBS system that operates with ultra-low pulse energies in the range of 10 - 200 nJ. To achieve this, we employ our home-built 2.8 GHz burst-mode Yb-doped fiber laser, which delivers ∼40 ps pulses to the sample with a beam diameter of around 18 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mtext>μ</mml:mtext> <mml:mtext>m</mml:mtext> </mml:mrow> </mml:math> . A systematic LIBS study was conducted on stainless steel (SS) under varying burst durations and burst energies to investigate 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.