By: Andreas Tünnermann
Today, there is a strong need for advanced micro machining tools due to the increasing miniaturization of components and systems. Application examples include the drilling of fuel injection nozzles or the structuring of thin film solar cells. However, the fabrication of structures with micrometer or even nanometer precision is a difficult task. Since a few years, pulsed laser systems are replacing conventional tools for micro machining like edm-machines. However, especially the precise laser micro structuring of metals is typically limited by thermal and or mechanical damage in the surrounding. Here, the ability of ultrashort-pulse lasers to fabricate precise micro structures on solid targets is opening new perspectives. In the past years, the superior quality of ablated holes and patterns produced by femtosecond or picosecond laser pulses compared to nanosecond pulses has been demonstrated. Although the production of high quality and high aspect ratio holes in metals with ultrashort laser pulses is still an open field of research, it already has significant technological impact on industrial applications.
Despite of these benefits, the industrial use of ultrashort pulse lasers has been hindered by their complexity and the limited processing speed which does not allow for cost-effective manufacturing. These disadvantages can be overcome by the novel regeneratively amplified solid state or fiber laser sources, providing high average powers and repetition rates.
Recently, we demonstrated in our laboratories ultrafast fiber amplifier systems with 800-W-average-power and mJ-level-pulse energies. These sources are very promising for industrial micro machining applications because of their compactness, high average power and high repetition rates that enable a significant increase of the processing speed.
Systematic studies of the effect of high repetition rates and high average powers on the processing speed and on the morphology of the structures have been performed. At high repetition rates heat accumulation effects leading to melting and increased heat-affected zones have been observed. In addition, plasma shielding effects have been measured. However, by using the high-power ultrafast fiber laser systems with optimized process control we have been able to machine high quality melt-free, and high aspect ratio micro structures within a few tens of ms. These results clearly demonstrate, that high average power ultrafast fiber amplifiers will open new avenues for the micro manufacturing of solid materials – most recent results will be reported.
The above brief overview was extracted from its original abstract and paper presented at The International Congress on Applications of Lasers & Electro-Optics (ICALEO) in Orlando, FL. To order a copy of the complete proceedings from this conference click here
Paper # M201