Flexible, compact and picosecond laser capable four-beam interference setup

Periodic micro structures on surfaces offer unique properties, such as hydrophobic behavior, holographic light reflection or friction and wear minimization. Multi-beam interference patterning is a technology to produce micro structures from several micrometers down to below 1 µm, dependent on the wavelength and angle between the interfering beams. A high power capable four-beam interference setup, designed for infrared ultrashort pulsed laser sources in the picosecond regime will be shown. The setup provides independent variation of the period, intensity distribution and pattern size of the interference pattern. The period is variable from 1 µm with a working distance of 100 mm up to 5 µm with a working distance of about 800 mm. The intensity distribution can be modified to different shapes, such as lines, holes, ripples etc. by controlling the polarization of each beam separately. The fluence of the pattern is controllable by changing the pattern size. To change the pattern size, the beam diameter can be varied by a telescope with variable focal length. The setup is built in a stable design of a size of about 300x300x300 mm³ and a weight of 4.6 kg. To avoid aberrations at high laser power, especially focus shift, the setup was designed with high reflective mirrors. An experimental verification shows the comparison between the experimental results and the calculated design and features