圆环衍射效应下涡旋光束的光强变化

为了分析拓扑电荷数以及相干性对部分相干涡旋光束的影响,利用部分相干光的统一理论和惠更斯-菲涅耳衍射原理,推导出随机电磁涡旋光束在自由空间中传播时,尤其是部分相干涡旋光束经圆环衍射后光强的计算公式,研究了部分相干涡旋光束通过圆环后的夫琅和费衍射特性。通过理论分析与数值计算表明,部分相干涡旋光束经圆环衍射后的光强分布情况与入射光的相干度、入射光束的拓扑电荷数、衍射孔径的大小等因素有关。当入射光束的拓扑电荷数越大,相干长度越长,衍射孔径越小时,衍射光束的光强分布会更加清晰,衍射效果也更加明显。

Change of intensity of vortex beam diffracted by a circular ring

For analyzing the influence of topological charge and coherence on the partially coherent vortex beam,the general formula was derived to calculate the intensity for a class of stochastic electromagnetic vortex beam while propagating in free space with the help of the unified theory of partially coherent beams and the Huygens-Fresnel principle,especially the class of partially coherent vortex beam diffracted by a circular ring.The Fraunhofer diffraction of a class of partially coherent vortex beam diffracted by a circular ring is investigated.It is shown that the intensity distribution will change after the beam transmitted through the circular ring,and the intensity distribution of the diffractive beam is related with the coherence of source,the topological charges of the source,and the size of the circular ring according to theoretical analysis and numerical calculation.For the source with higher topological charges,better coherence and smaller size of the circular ring,the intensity distribution of the diffractive beam shows more clearly and the diffractive effect is more evident.