Precision beam shaping by spatial frequency filtering

Flattop beams are in high demand for a variety of applications, including uniform surface treatment, interference laser processing, repairing and skin therapy. In this experiment, we optimized the direction of phase grating to spatially separate the beam into extracted and residual components in the Fourier plane, and spatially filtered the components to form a square or hexagonal flattop beam with no wave-like structure inside and high edge steepness.