Beam shaping using two spatial light modulators for ultrashort pulse laser ablation of metals

In this study, an optical setup based on two phase-only spatial light modulators is presented, capable to shape two parallel laser beams. Each of the light modulators creates different and complementary Gaussian multi-spot distributions in the focal plane. By the polarization based combination of two differently shaped beams, a multi-spot beam profile with higher multi-spot density than for a single spatial light modulator setup can be obtained without speckles to appear. Beam shaping results are characterized by means of a beam profile camera and compared to a single spatial light modulator setup. Beam shapes generated by the presented setup are applied to ultrashort pulse laser ablation of metals. The potential of the presented optics is discussed regarding ground roughness and waviness of the ablated structure.