Fig. 1. Flow chart of traditional GS algorithm

Fig. 2. Improved GS algorithm flow chart

Fig. 3. Flow chart of iterative optimization algorithm

Fig. 4. The curve of iterative optimization

Fig. 5. The RMSE and diffraction efficiency

Fig. 6. The simulation results of the square flat-topped beams

Fig. 7. Phase unwrapping diagrams and phase unwrapping transversals

Fig. 8. Experimental setup

Fig. 9. Experimental results

Fig. 10. The influence of phase parameters on the output spot

Fig. 11. Influence of incident Gaussian beam waist radius on output spot

Fig. 12. The effect of incident Gaussian beam and DOE center deviation on the output spot

Fig. 13. Influence of manufacturing tolerance of DOE on spot quality