Diffraction-Based Strategy for Monitoring Topographical Features Fabricated by Direct Laser Interference Patterning

Process monitoring in laser-based manufacturing has become a forward-looking strategy for industrial-scale laser machines to increase process reliability, efficiency, and economic profit. Moreover, monitoring techniques are successfully used in laser surface texturing workstations to improve and guarantee the quality of the produced workpieces by analyzing the resulting surface topography. Herein, dot-like periodic surface structures are fabricated on stainless steel samples by direct laser interference patterning (DLIP) using a 70 ps-pulsed laser system at an operating wavelength of 532 nm. A scatterometry-based measurement device is utilized to indirectly determine the mean depth and spatial period of the produced topography by analyzing the recorded diffraction patterns. As a result, the average depth and the spatial period of the dot-like structures can be estimated with a relative error below 15% and 2%, respectively. This new process monitoring approach enables a significant improvement in quality assurance in DLIP processing.