Ablation characteristics of Au, Ag, and Cu metals using a femtosecond Ti:sapphire laser

Femtosecond laser ablation of metallic bulk crystals of Au, Ag and Cu was experimentally studied with laser pulse widths ranging from 120 fs through 800 fs at a center wavelength of 780 nm for micro-machining applications. Two different ablation regimes were found in terms of the laser fluence. The characteristic length of different ablation regimes was explained in terms of the optical skin depth and thermal diffusion length; it was determined by the peak electron temperature in the two-temperature model. The lateral feature of the two ablation regimes is discriminated by the amount of particles accumulated by the evaporation process. Ablated particle was observed less in the lower fluence regime than in the higher fluence regime, but there was no significant difference on the ablated surface. The parameters used in the two-temperature model, are discussed in order to model the ultrashort pulsed laser ablation process theoretically. It is shown that the obtainable range of the lower fluence regime is enhanced with the shorter pulse lasers, because the ablation etch rate is decreased with longer pulse width.