Speckle-reduced diffractive optical elements beam shaping with regional padding algorithm

Diffractive optical elements (DOEs) have been widely used to realize beam shaping. However, the speckle noise always appears in the reshaped beam, which induces beam quality degradation. We proposed a regional padding algorithm based on the Gerchberg–Saxton algorithm to implement speckle-reduced beam shaping. A variable region is set in the DOE to iterate and optimize the phase of each part DOE. Zero padding is used around the DOE to decrease the sampling interval on the output plane. When the region expands and padded value reduction is controlled slowly, more sampling points on the output plane can be optimized effectively and suppress speckle noise. Numerical simulations and optical experiments have been performed to verify the feasibility of the proposed method.