From Event: SPIE LASE, 2019
Laser processing using femtosecond laser pulses has been emerging as a powerful tool for micromachining and surface functionalization owing to its precise processing capability, and the understanding of light-matter interactions is of great importance for the optimization. One big challenge in understanding laser ablation processes during microprocessing is to understand influences of surface morphology, which can substantially change the light-matter interaction. Pulses after the first shot experience changes in the surface morphology that are induced by the prior pulses during multi-shot irradiation. To investigate the relation between the surface morphology and the laser ablation processes during multi-shot irradiation, we developed an in-situ three-dimensional depth profile measurement system with nanometer precision. Our system enabled pulse-by-pulse monitoring of the surface morphology changes so that we can investigate the changes in depth profile induced by laser ablation during multi-shot irradiation.
The experimental system consisted of a 1-kHz femtosecond laser, and a white-light interferometry microscope, which was synchronized with the regenerative amplifier. Notably, the changes in the depth profile less than a few tens of nanometers were precisely measured, and the changes strongly depended on the original surface morphology and the laser fluence. We performed systematic measurements on the changes in depth profile as a function of laser fluence and the number of irradiated pulses with various material, and conclude that laser-induced embrittlement of a target material plays a decisive role to determine the ablation rate during multiple-pulse irradiation.
© (2019) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Shuntaro Tani and Yohei Kobayashi, "Pulse-by-pulse surface structure evolution during multiple-pulse femtosecond laser ablation (Conference Presentation)," Proc. SPIE 10906, Laser-based Micro- and Nanoprocessing XIII, 1090602 (Presented at SPIE LASE: February 05, 2019; Published: 4 March 2019); https://doi.org/10.1117/12.2506147.6008600414001.