Design of the continuous phase plates for beam smoothing

Aiming at the special requirements such as homogeneous intensity, high ratio of applied energy and small sidelobe for the focal spot of drive source in large-sized laser device, a hybrid method based on geometrical transformation and modified Gerchberg-Saxton (G-S) algorithm was proposed to design continuous phase plates(CPP).The performance of the CPP was verified by means of diffraction numerical integrating method and the result showed that the CPP obtained good 24th-order super-Gaussian fit with diffractive efficiency up to 99.79%, top mean square error of 0.35% and top modulation of 1.33%.This method is fast and avoiding the shortcoming that the G-S result is easy to trap in local optimum.Moreover, the designed plate is fully continuous, so the plate is easy to be fabricated and improves the smoothing performance of the plate.