Signal Enhancement and Reproducibility Improvement in Double-Pulse Femtosecond-Laser-Induced Breakdown Spectroscopy

Abstract

A focus depth optimization method was proposed for signal enhancement and reproducibility improvement in pump-probe collinear double-pulse femtosecond laser-induced breakdown spectroscopy. This method was based on the optimization of the focus depth of the second pulse. The spectral signal intensity showed a stable enhancement with an enhancement factor of ~3, and the signal reproducibility exhibited minimal fluctuations when the focus depth of the second pulse was within the range of 0–2 mm below the sample surface. Additionally, the possible mechanisms behind the observed signal enhancement and improvement in reproducibility were discussed based on the measured plasma temperature and electron density.