Optimization algorithm for flattop beam shaping using analytically initial phase

Accurate control over light field distribution is of great importance to laser-based technologies. Here, an improved Gerchberg-Saxton (GS) algorithm is proposed to calculate the diffraction phase for flattop beam generation. In comparison with GS algorithm with a random phase as the initial phase of the iteration process, an analytical phase with a circular phase distribution is employed as the initial phase in the proposed algorithm. It is verified that the proposed algorithm can be used to generate flattop beams with improved uniformity and energy utilization ratio. Furthermore, both speckle noises and the ringing effect are effectively suppressed. We believe that the proposed diffraction phase optimization algorithm can be widely applied to high-quality beam shaping applications.