Ultrashort laser ablation of metals

The characterization of a plasma plume is a key issue in laser ablation and deposition studies. Combined diagnostic measurements by Optical Emission Spectroscopy, Fast Imaging have been used to study the dynamics and composition of laser ablation plume produced during ultrashort laser irradiation of metals, in vacuum. Our results show that, in the laser fluence range of 0.1-1.0 J/cm(2), the process of matter removal results in a plasma plume which is mainly composed of two different populations: atoms and nanoparticles. The nanoparticles dynamics during expansion has been analyzed through their structureless continuum optical emission, while atomic species have been identified by their characteristic emission lines. The presence of a fast atomic component emitted from the sample surface as a result of the supercritical state induced by the intense ultrashort laser pulse irradiation has been also observed both by optical emission spectroscopy and fast imaging techniques. Finally, atomic force microscopy analysis of the material deposited at room temperature has allowed the characterization of the nanoparticles size distribution.