经光阑衍射的平顶涡旋光束位相奇点的演化特性

推导出了平顶涡旋光束通过有光阑ABCD光学系统的传输解析式,并以光阑透镜和矩形光阑系统为例,与平顶光束比较研究了截断参量、相对离轴距离和光束阶数对衍射场中位相奇点演化特性的影响.数值计算表明,平顶涡旋光束通过上述光学系统均存在位相奇点,即使源处涡旋被光阑阻拦时,衍射场中也会出现位相奇点;而平顶光束通过光阑透镜系统存在刃型位错,随着截断参量增大,会发生刃型位错的演化和湮灭现象,且平顶光束通过矩形光阑系统没有发现位相奇点.

Evolution of Phase Singularities of Flat-topped Vortex Beam Diffracted by an Aperture

The analytical expression for the propagation of flat-topped vortex beam through an aperture paraxial optical ABCD system is derived. Taking aperture lens and rectangular aperture as typical examples, evolution of phase singularities between flat-topped vortex beam and flat-topped beam is comparatively studied. The effect of the aperture truncation, relative off-axis displacement and beam order on evolution of phase singularities is illustrated by numerical examples. The results show that there always exists phase singularities for flat-topped vortex beam through an aperture, and the phase singularities take place in the diffracted field even the vortex core is stopped by the aperture. However, numerical calculations show that edge dislocations appear for flat-topped beam through aperture lens, and the evolution and annihilation of the edge dislocations take place with increasing of truncation parameter, while the phase singularities are not found for flat-topped beam through rectangular aperture.