Surface Modification of Copper by MHz Burst Laser Irradiation

Ultrafast lasers containing burst packets with pulse separations in the MHz range have been widely studied for drilling [1], smoothing [2], plasmonic coloring [3], and creating micro- and nanostructures. At these intra-burst pulse separations, laser-mater interactions can be affected by plasma cloud formation, heat dissipation, and the ejection of particles [4]. The interaction of bursts containing different numbers of pulses has been studied in literature mainly by characterizing material removal rates [4], with the resulting surface structuring remaining mostly unexplored. Herein, the effect of even and odd numbers of pulses within burst packets is studied in copper, focusing on the mechanisms behind optical and morphological surface modifications.