No abstract

The aim in ultrashort‐pulsed materials processing is generally to keep interactions between the effects of the individual laser pulses to a minimum in order to minimize quality‐reducing effects and to avoid exceeding process‐specific thresholds. A contrasting approach aims at exploiting the interaction of consecutively applied laser pulses with the respective material response. In this case, it is possible to use particularly high average laser powers as well as bursts that feature time intervals of only a few nanoseconds.

Ultrashort laser pulses are often used in industrial manufacturing due to the small heat-affected zones they produce and their low melt formation. A contrasting approach aims to exploit the residual heat of successively applied laser pulses in combination with the material response. As a result of the heat accumulation within a burst, the formation of a melt film that is highly spatially and temporally confined is possible. Experiments, theoretical analysis, and numerical heat-flow simulations are used to show the influence of the laser parameters on pulsed melting and surface structure formation. Special attention is paid to the temporal delay between the pulses. A comparison of the process on iron and titanium allows the influence of material properties to be considered.

The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adpr.202200045.

The combination of direct laser interference patterning (DLIP) with laser-induced periodic surface structures (LIPSS) enables the fabrication of functional surfaces reported for a wide spectrum of materials. The process throughput is usually increased by applying higher average laser powers. However, this causes heat accumulation impacting the roughness and shape of produced surface patterns. Consequently, the effect of substrate temperature on the topography of fabricated features requires detailed investigations. In this study, steel surfaces were structured with line-like patterns by ps-DLIP at 532 nm. To investigate the influence of substrate temperature on the resulting topography, a heating plate was used to adjust the temperature. Heating to 250 $$^{\circ }$$ ∘ C led to a significant reduction of the produced structure depths, from 2.33 to 1.06 µm. The reduction is associated with the appearance of a different LIPSS type, depending on the grain orientation of the substrates and laser-induced superficial oxidation. This study revealed a strong effect of substrate temperature, which is also to be expected when heat accumulation effects arise from processing surfaces at high average laser power.