Improved Efficiency of an Adaptive Beam-Shaping Technique Based on Phase Gratings and Spatial Frequency Filtering

Flattop beam shapes are in high demand for various laser applications, including ultra-high-power laser systems and surface processing, which includes interference laser processing and medical treatment. In this study, we report on the improvement of extraction efficiency in a beam shaping method using phase gratings and spatial frequency filtering. By organising the phase grating vector kkgg unparallel to the normal vectors kknn of the sides of an aimed polygonal beam shapes, which are square and hexagonal in this study, the high-spatial frequency component is maintained in the spatial frequency filtering process, and high-quality beam shaping with good flatness and edge steepness can be obtained. In addition, the extraction efficiency of polygon-shaped beams from a Gaussian beam or flattop circular beam is discussed.