Uniformity of near-field caused by continuous phase plates for beam smoothing

A theoretical model for calculating the near field caused by continuous phase plates (CPP) applied in high-power laser system is built up for decreasing the laser induced damage probability of the elements behind CPP. The distribution of near field caused by CPP is calculated and analysed using this model, and the effect on the uniformity of the near field caused by the intensity modulation of input beam, interference and diffraction from CPP is analysed. The simulative and analytical results show that the interference ,the diffraction and the input beam quality affect the uniformity of the near field, and the input beam affect the beam quality of CPP more severely than the interference and diffraction when the beam quality is bad, but the interference and diffraction will decrease the uni