| Abstract [eng] |
Laser micromachining is an appealing processing method because of the abundance of applications such as laser colouring and laser polishing. Laser colouring is surpassing traditional colouring techniques due to its versatility and eco-friendliness. Similarly, laser polishing is gaining popularity for offering high precision, material versatility, and the ability to polish and micromachine with the same system. This thesis explores laser colouring and polishing of stainless steel and copper mainly using MHz, GHz, and biburst modes. GHz bursts produced the widest spectrum of vivid colours due to oxidation, achieving the highest reported colouring rate of 42.5 mm²/s. The process allows multi-colour patterning of complex shapes. Moreover, stainless steel samples exhibited nanostructured surfaces with hydrophobic properties, while grayscale colouring and wettability control were demonstrated on copper. The study also investigated the impact of copper oxide transparency on lift-off thresholds due to nonlinear and saturable absorptions. For laser polishing, GHz bursts provided the smoothest surfaces, particularly for copper with a surface roughness of less than 0.10 µm due to increased heat accumulation. Additionally, laser ablation showed bi-stability in surface roughness, influenced by shielding and re-deposition effects. |
