Ultrashort Pulse Laser Ablation of Bulk Materials Using Shaped Laser Beams

Book excerpt: High precision, high quality, and high throughput of ultrashort pulse laser ablation of bulk material are the most demanded properties that are required to let this process technology compete with other micro-machining techniques. Previous attempts to increase volumetric ablation rates of ultrashort pulse laser processes were based on the increase of fluence or pulse repetition rates. They run into limitations mainly set by the occurrence of bumpy surfaces due to overheating of bulk material. In this work, the potential of laser beam shaping for the enhancement of ablation rates is studied systematically for the first time. The question regarding the physically shortest possible process time for ablation of 2.5D-structures by means of an ultrashort pulse laser is answered using a heat conduction model, which is extended by the ability to consider spatially shaped beams. The strategy of laser beam stamping is implemented in a novel optical setup and proven both theoretically and experimentally to have a great potential for increasing ablation rates.