Surface Structuring with Ultra-short Laser Pulses: Basics, Limitations and Needs for High Throughput

TLDR

Ultra‑short pulsed lasers have become industrially attractive as high‑power systems enable high‑throughput processing, but achieving optimal surface structuring requires an optimized process strategy and operating at the fluence that maximizes ablation efficiency. The study aims to identify process conditions that maintain high machining quality while operating at the efficiency optimum, which requires either impractically high marking speeds or large spot areas. Removal rate scales with average power and depends on threshold fluence, penetration depth, material properties, pulse duration, and incubation effects, and can be increased by using multi‑spot patterns generated with diffractive optics or spatial light modulators.

Abstract

The interest using ultra-short pulsed laser systems for industrial applications increased remarkably as reliable high power systems with average power exceeding several 10W became available, facilitating the development of high throughput processes. Exhausting the potential of these systems demands an optimized process and an adapted process strategy as well. For surface structuring it can be shown that in case of metals and many other materials, the ablation process itself shows a maximum efficiency at an optimum fluence. The corresponding removal rate directly scales with the average power and depends on the threshold fluence and the energy penetration depth into the material. These parameters are material depending but they change with the pulse duration and are also subject to incubation effects. Working at the optimum point with highest efficiency and keeping the high machining quality sets conditions for the process strategy which can only be fulfilled by either very high marking speeds, not available with common beam guiding systems, or high spot areas as they can e.g. achieved with multi-spots by a diffractive optical element or a spatial light modulator.