Dependence of silicon ablation regimes on fluence during ultrafast laser irradiation

Abstract

AbstractModels and experiments were developed to study femtosecond laser ablation of silicon using 800 nm, 40 fs pulses with fluences ranging from 0.5 to 35 J/cm2. At low fluences, ablation was found to occur due to bubble formation and splashing within the melt layer. At higher fluences, it was found that the ablation depth exceeded the melt layer depth due to shockwave ablation. The variation in ion flux and ion velocity was also studied both experimentally and theoretically. It was found that the variation in ion flux is mainly dependent on the variation in the average charge state, with only a small variation in the total number of ions above $\sim \!\!1.5\; \,{\rm J/c}{{\rm m}^2}$. Comparisons between the theoretical and experimental ion flux showed that higher charge state ions received greater portion of the laser energy compared with lower charge state ions.