Analysis and evaluation of boundary conditions for direct surface structuring by multi-beam interference

Multi-Beam-Interference (MBI) is a promising approach for a more cost-efficient functionalization of surfaces by nano structuring. It allows the simultaneous structuring of a whole surface area in one process step. This area is directly laser ablated with the modulated intensity created by the interference of two or more coherent beams. In this study, we first analyze the different possibilities for MBI setups with regards to the number and the alignment of utilized beams used for direct surface structuring. The key factors for direct surface structuring are stability and contrast of the interference pattern. From these criteria 2-Beam interference is derived as optimal setup for the direct structuring of surfaces. In the second part of this work experiments with a ns- and a ps-laser are carried out and compared to the theory. For the ns-laser minimal structures sizes in the 100 nm regime on polyimide are feasible, for the ps-laser minimal periodicity of 400 nm on stainless steel. The measured interference contrast decreases significantly for shorter pulses.