Investigating the influence of pulse duration in burst mode ablation of stainless steel

Researchers have studied the micro-structuring of metals using ultrashort laser pulses in experimental and theoretical investigations for many years for various industrial applications. It has been a major challenge, however, to convert the maximum available power with a high throughput on the material and ensure the economic efficiency due to the rapid development of increasingly powerful ultrashort pulse laser sources

Lickschat et al. investigate the influence of the pulse duration on the efficiency and quality of the ablation process by using the megahertz burst.

“In this work, we seek to combine the excellent smoothing effect of the burst mode with the high removal efficiency that occurs with ultrashort laser pulses with pulse durations in the femtosecond range,” said author Peter Lickschat.

In the study, stainless steel was processed in the MHz burst with a solid-state laser capable of varying the pulse duration from .27 picoseconds to 10 picoseconds. The laser also generated bursts with an intra-burst pulse repetition frequency of 65 MHz with up to nine pulses per burst.

The researchers found the ablation efficiency in the femtosecond regime was significantly higher than compared to pulse durations in the picosecond regime. They identified a smoothing effect for a certain number of pulses in the burst depending on the fluence and the pulse duration efficiency. In the so-called MHz burst, the accumulation of residual heat produced a melt film, which also influenced the smoothing effect.

The researchers plan to implement the results to generate 3D microstructures with excellent surface qualities, which would be applicable in medical technology, laser engraving, laser polishing and laser micromachining in the field of flow-optimized microcomponents.

Source: “Burst mode ablation of stainless steel with tunable ultrashort laser pulses,” by Peter Lickschat, Daniel Metzner, and Steffen Weissmantel, Journal of Laser Applications (2021).The article can be accessed at https://doi.org/10.2351/7.0000271 .