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.

Picosecond laser microvia drilling of ABF material using MHz burst mode

“…The decrease of the ablation thresholds for both materials with an increasing number of intra-burst pulses is attributed to the incubation effect [29,50,51]. This phenomena is ascribed to the accumulation of laser-induced chemical and structural changes as well as plastic deformation of the substrate as a result of thermal stress fields [52,53].…”

“…Consequently, the arising laser pulse energies of up to some 100 μJ lead to a laser fluence that is significantly above the well-known optimum for maximizing the ablation efficiency and rate [24]. For scaling the laser pulse energies closer to the optimum ablation efficiency, so-called laser burst mode can be used to split a laser pulse into at least two and typically up to a few hundred intra-burst pulses with a temporal intra-burst interval in the nanosecond regime [24][25][26][27][28][29][30][31].…”

A new Network Simulation Method for the characterization of delay differential equations

“…In this work we characterize for the first time the delay dependence for the NSM, which immediately opens new applications to the method. We will illustrate the implementation of the delay terms in the electrical analogy through the employment of a first order delay equation, the Hutchinson's model, and we will apply the approach to two practical examples of interest: (a) adsorption kinetics with time delay, extendable to the oscillatory molecular adsorption patterns in proteins [3], and (b) modeling of pulse width in quantum dot mode-locked lasers (QDMLLs), essential for communication, medical, micromachining and military applications, among others [18][19][20][21][22]. Additionally, we will compare the results with those obtained with software Mathematica [23], showing that they are orders of magnitude faster.…”