Heat accumulation is one of the major challenges in using 100 W megahertz class ultrashort pulse lasers (UPL) for machining applications with very high throughput. Thermal effects are detrimental to UPL characteristic high-quality machining, like cutting or engraving, preventing the wider use of UPL in industrial environments. Mincuzzi et al. developed a beam engineering strategy to help mitigate these thermal effects.

Both high scan speed and high accuracy are considered necessities for laser machining. By using a very fast and highly accurate galvo scanner – a type of motorized mirror – to deliver the laser beam at speeds about an order of magnitude faster than traditional scanners, the group was able to achieve a very good machining quality while increasing the repetition rate and the output power of the UPL. In the case of a linear cut, they demonstrated a reduction in the processing time by more than a factor of 30.

In a second test, the authors considered the cutting of millimetric gears and split the beam into multiple sub-beams for parallel processing. This setup increased the throughput tenfold while maintaining machining quality.

“We have been playing with heat as you can play with fire, and we didn’t get burned!” said author Girolamo Mincuzzi.

Because heat effects are the most detrimental for smaller workpieces, the authors are primarily focusing the applications of this work on precision micromechanics, such as watch fabrication.

“I see clearly that our approach can be extended to processes like surface structuring or texturing, dicing and scribing, which are widely diffused from electronic to tooling as well as the food industry,” Mincuzzi said.

Source: “Beam engineering strategies for high throughput, precise, micro-cutting by 100 W, femtosecond lasers,” by Girolamo Mincuzzi, Alice Rebière, Marc Faucon, Aurélien Sikora, and Rainer Kling, Journal of Laser Applications (2020). The article can be accessed at https://doi.org/10.2351/7.0000174.