高斯光束经过多阶螺旋相位板后光束特性研究

Analysis on the Beam Characteristic of Gaussian Beam Passing Multi-Level Spiral Phase Plate

由光束的近轴传输理论,推导了高斯光束经过多阶螺旋相位板(SPP)后电场的解析表达式,在此基础上对高斯光束通过多阶螺旋相位板后的光强分布和相位分布分别进行了分析。研究发现,和理想的螺旋相位板不同,高斯光束经过多阶螺旋相位板后光强分布具有角向周期性,周期数与相位板阶数相等。阶数为16时,产生涡旋光束的光斑质量、相位质量比较合适。在相同的情况下,获得较好的相位质量需要更长的传输距离。另外,相位板所提供的拓扑荷数对以上问题影响不大,真正起决定作用的仍然是相位板的阶数。该结论能对实验中SPP的使用提供指导作用。

Based on the paraxial approximation of propagation of optical beam, the analytical expression of electric field is derived on the observation plane for the Gaussian beam passing through spiral phase plate （SPP）. Based on the derived result, the intensity and phase distributions of the generated Gaussian vortex beam by SPP are analyzed. It is found that, different from the case of ideal SPP, the intensity of the beam from multi-level SPP is periodically distributed in the azimuthal direction. The periodicity is equal to the order of the SPP. A suitable choice of the SPP is 16-level structure to obtain good quality of intensity and phase distributions of the generated vortex beam. On the same condition, obtaining good quality of phase distribution requires longer propagation distance of the beam after SPP. In addition, the topological charge decided by the SPP has almost no influence on the above points. The decisive element is still the order of the SPP. The results can provide guidance on the use of SPP in the experiment.