Transient electron excitation in laser-induced plasma-assisted ablation of transparent materials

We investigate the mechanism of laser-induced plasma-assisted ablation (LIPAA), by which high-quality and high-efficiency ablation of transparent materials, such as glass, can be performed with a single conventional pulsed laser. The laser-induced plasma induces transient absorption of the laser beam $(532nm)$ by the glass substrate. The origin of the transient absorption is electron excitation by ions with kinetic energy more than approximately $10eV$ in the plasma, which is observed by measuring transient polarization change in the glass substrate applied with a high external pulsed electric field during the plasma-assisted electron excitation (plasma-conductivity measurement). A possible mechanism of LIPAA is proposed based on the results obtained.