Sidelobe suppression in the generation of beam carrying orbital angular momentum

We propose a method to generate vortex beam with sidelobe suppression by adding an axicon before the spiral phase plate (SPP). In this paper, the far-field diffraction model of the SPP is theoretically analyzed in detail. The numerical simulation results show that the quality of the generated beam which carries the orbital angular momentum is improved dramatically. What's more, we also study the effect of the radius of the annular beam on the performance of sidelobe suppression.