Darkening of metal surfaces by nanosecond pulsed laser ablation

Abstract

We applied nanosecond pulsed laser ablation to reduce the reflectivity of metal surfaces. The change in reflectivity was studied at different laser scanning pitches (i.e., pulse number densities) and the trends obtained were correlated with the morphological and compositional changes induced by the ablation. In the case of copper, we found that it wasn’t the laser etching itself that caused the darkening of the surface, but rather the nanoclusters and nanoparticles produced in the cooling ablation plume as they fell back onto the surface. Our model calculations confirmed the role of micro- and nanostructures and the presence of copper oxides in reducing the reflectivity of ablated copper.