MHz burst mode processing as a tool for achieving removal rates scalability in ultrashort laser micro-machining

Abstract The average power of ultrashort laser source has been increasing continuously and, therefore, solutions are required to employ fully these technology advances for improving the ablation efficiency in laser micro-processing. The use of burst mode processing is one of the solutions that has attracted a significant research and industrial interest in the past decade. A novel empirical methodology is proposed and implemented in this research to assess the MHz burst mode impact on the specific removal rate (SRR) and processing efficiency in ultrashort laser micro-machining. Especially, the capability of the MHz burst mode processing is investigated to scale up SRRs achievable on copper and stainless steel while utilising fully the available maximum pulse energy and average laser power. The results showed that the MHz burst mode offer a significant SRR scalability potential that can be attributed to beneficial near optimum fluence level and other side effects such as heat accumulation. Also, it is evidenced from the obtained results that the surface quality attained with the burst mode processing was comparable to that achieved with the single-pulse processing and even better at some specific process settings. Thus, the obtained SRR improvements were not in expense of the surface quality and the MHz bust mode processing represents a promising solution to employ fully the constantly increasing average power in ultrashort laser processing operations.