Large-angle programmable direct laser interference patterning with ultrafast laser using spatial light modulator

Direct laser interference patterning (DLIP) facilitates the creation of periodic micro- and nanostructures for numerous applications such as anti-reflective moth-eye structures, security features (holograms) or for surface topology modification. For high quality applications the use of ultrafast laser sources is demanded. However, this puts high requirements on laser system technology as the short pulses imply very short spatial interaction lengths. Furthermore flexible adjustment of the patterns to be generated is preferable which is difficult with most opto-mechanical setups. We present an approach using a spatial light modulator (SLM) for the creation of flexibly programmable DLIPpatterns. With our optical setup we are able to overcome the limitations the SLM poses at the current state of the art, thus achieving 45-90 interference angles of two-, three- and four-beam interference patterns. We show regular structure sizes of,-1 m inscribed on the surface of polished metallic substrates with a 12 picosecond laser source at a wavelength of 1064 nm.