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.
In this study, a scatterometry-based monitoring system designed for tracking the quality and reproducibility of laser-textured surfaces in industrial environments was validated in off-line and real-time modes. To this end, a stainless steel plate was structured by direct laser interference patterning (DLIP) following a set of conditions with artificial patterning errors. Namely, fluctuations of the DLIP process parameters such as laser fluence, spatial period, and focus position are introduced, and also, two patterning strategies are implemented, whereby pulses are deliberately not fired at both deterministic and random positions. The detection limits of the system were determined by recording the intensities of the zero, first, and second diffraction order using a charge-coupled device (CCD) camera. As supported by topographical measurements, the system can accurately calculate spatial periods with a resolution of at least 100 nm. In addition, focus shifts of 70 µm from the optimum focus position can be detected, and missing patterned lines with a minimum width of 28 µm can be identified. The validation of this compact characterization unit represents a step forward for its implementation as an in-line monitoring tool for industrial laser-based micropatterning.
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