High-Efficiency Sub-Micrometer Multi-Beam Interference Structuring for Large-Scale Surface Using Ultrashort Laser Pulses

Laser direct structuring using multi-beam interference can fabricate one and two-dimensional periodic patterns with a structural periodicity from hundred nanometer to tens of micrometer. Nevertheless, the structuring efficiency, which is relative to patterning speed, structure periodicity, depth and laser fluence applied, and homogeneity of interference pattern are still the main concerns and need to be taken into consideration especially for large-scale surface. In this paper, the structuring efficiency of two beam interference was defined and was investigated on tool steel using an ultrashort pulsed (USP) laser. During the multi-beam interference structuring, the USP laser, which has a pulse width of 10 picoseconds, worked at a wavelength of 532 nm and repetition rate of 100 kHz. Linear patterns with a periodicity of 940 nm and was fabricated on an area of 100 mm x 100 mm. We achieved a patterning speed up to 500 mm/s on the surface of tool steel by means of an x-y linear working stage. The local morphology was analyzed by an atom force microscopy (AFM). Moreover, the global homogeneity of the patterned surface was quantitatively characterized. The results demonstrated a stable structuring process with minor deviation of structure periodicity and depth.