Automated spatial period variation for direct laser interference patterning

Abstract

In recent years, various studies have described the potential of Direct Laser Interference Patterning (DLIP) technology for technical surfaces in industrial applications. The focus of the studies is currently on the variability of the structural patterns (also in combination with Direct Laser Writing processes), the increase of the aspect-ratio and the upscaling to high processing speeds as well as large area structuring using mainly laser-scanner systems. Common are spatial periods of a few microns. However, for some DLIP applications regarding the structuring of tool steel the focus is different. Namely it can be beneficial to achieve a variable spatial period while maintaining a well-defined structure. Examples are molding or embossing processes where the structured tool steel is used as a template. Again, the spatial periods ranges in the magnitude of micrometers or below. This study describes the development of an automated system technology for a high-precision DLIP setup without using a laser-scanner-system. Two coherent beams from a beam source with ultrashort laser pulses of 10 ps and a wavelength of 532 nm are superimposed on a metallic workpiece to ablate line-like periodic patterns by interference. The characteristic spatial period created in the process is dependent on the incident angle between the two beams. It can be varied in the micro- and sub-micrometer range by implementing axes to automate the beam guidance and subsequently controlling the incident angle. The setup is calibrated and fine-tuned in a process where the spatial periods structured at different incident angles are validated using an Atomic Force Microscope (AFM). Further automation is achieved by developing a user interface for intuitive control. Finally, various spatial periods are structured onto tool steel for industrial applications in the field of the automotive industry.