Abstract
Due to high power and ultrashort pulses, femtosecond lasers excel at (but are not limited to) processing materials whose thicknesses are less than 500 microns. Numerous experiments and theoretical analyses testify to the fact that there are solid grounds for the applications of ultrafast laser micromachining. However, with high costs and complexity of these devices, a sub-picosecond laser that might be an alternative when it comes to various micromachining applications, such as patterns and masks in thin metal foils, micro-nozzles, thermo-detectors, MEMS (micro electro-mechanical systems), sensors, etc. Furthermore, the investigation of sub-picosecond laser interactions with matter could provide more knowledge on the ablation mechanisms and experimental verification of existing models for ultrashort pulse regimes. In this article, we present the research on sub-picosecond laser interactions with thin aluminum foil under various laser pulse parameters. Research was conducted with two types of ultrafast lasers: a prototype sub-picosecond Yb:KYW laser (650 fs) and a commercially available femtosecond Ti:S laser (35 fs). The results show how the variables such as pulse width, energy, frequency, wavelength and irradiation time affect the micromachining process.
Highlights
A scientific goal of this study is a better understanding of the physical phenomena and identification of ablation mechanisms in sub-picosecond regimes
In the materials undergoing laser micromachining, there are various markers that can be connected. As it was previously stated, ablation mechanisms strongly depend on the laser beam parameters to the dynamical mechanisms and the ablation threshold
Once a certain energy level is achieved, the curve begins to flatten. With both crater width and depth increasing with the laser fluence, the increase in the heat affected zone was small or non-existent in the sub-picosecond regime
Summary
A scientific goal of this study is a better understanding of the physical phenomena and identification of ablation mechanisms in sub-picosecond regimes. An effective micromachining process depends on the laser beam parameters, such as pulse duration, wavelength, energy, frequency or irradiation time, as well as target material properties [2]. These parameters affect the course of laser ablation, which engages different mechanisms than longer, i.e., picosecond and nanosecond, pulses [3,4]. We found this region between picosecond and femtosecond laser pulses interesting for further investigation, since both short and long pulse interactions with matter may appear
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