Femtosecond GHz bursts for surface laser polishing

Surface roughness is crucial for various applications like injection molds for optical components, medical implants, and additively manufactured parts. Burst laser polishing is an advantageous technique as it allows precise and controlled depth material modification. During laser irradiation, the molten material flows from peaks into the valleys due to surface tension, as a result smoothening the surface. The idea of this work was to test the GHz burst capabilities to smooth the surfaces of metals and semiconductors. In the case of silicon wafer polishing, the surface roughness Sa of the initial non-polished wafer was reduced more than three times by multiple scans. The polishing effect was clearly visible due to increased reflection of the wafer surface. In the case of stainless steel polishing, the GHz burst mode was able to erase the Laser-Induced Periodic Surface Structures (LIPSS), which were formed during conventional single-pulse laser ablation. This technique expands the applicability of ultrashort pulse technology in manufacturing areas where mirror-like polished surfaces are required.