Complex diffractive surface patterns on metals by UV-ps laser ablation.

Diffractive surface patterns with complex textures are generated on metal surfaces by picosecond UV laser ablation using an interference setup. Two diffraction gratings with variable distance and rotation angle provide a huge variety of interference patterns and thus resulting surface topographies. This variety can be further enhanced by selecting or blocking particular beams. A correlation analysis of the complex diffraction patterns generated by reflection of visible laser light at these surface topographies demonstrates that patterns with slightly differing fabrication parameters (variation of 0.5 mm in distance or 1° in rotation) can be clearly distinguished.