Measuring Method for the Interference Contrast of Multi-Beam-Interference

Abstract

Multi-Beam-Interference (MBI) is a promising approach for the direct nano structuring of surfaces. An important characteristic of MBI is the interference contrast which describes the modulation depth of the intensity distribution. While theoretical calculation for the interference contrast exists in literature, no actual measurement in experiments is documented. In this paper we present a method for determining the interference contrast by measuring the virtual shift of the ablation threshold. This virtual shift is caused by the modified intensity distribution via interference. At first, the theoretical basis for the measuring method is introduced, secondly the method is tested with a two beam interference setup used for direct structuring of surfaces. The measuring method shows consistent results and proves to be a useful tool for characterization of the interference pattern.