随机电磁涡旋光束的深聚焦特性

基于德拜矢量积分理论,研究了随机电磁涡旋光束经过大数值孔径透镜之后的聚焦特性及透镜的数值孔径、入射光束的偏振度、拓扑荷以及横向相干长度对焦平面附近聚焦光束的光强分布和相干度的影响.结果表明:适当地选择相关参量,可在焦平面上得到椭圆形光斑的光强分布以及平顶光强分布.随机电磁涡旋光束在焦平面上同一点处两个相互垂直分量之间的相干度,不同两点处两个相同分量之间的相干度以及不同两点处两个相互垂直分量之间的相干度研究表明,入射光束的拓扑荷和横向相干长度对聚焦光束的相干性有着十分明显的影响.

Tight Focusing of Stochastic Electromagnetic Vortex Beams

Based on vectorial Debye theory, the focusing properties of stochastic electromagnetic vortex beams by a high numerical aperture objective are investigated. The influence of numerical aperture of the objective, the degree of polarization, the topological charges, and the transverse coherent length of the incident vortex beam on the intensity and spectral degree of coherence in the focal region are investigated. Studies in intensity distribution reveal that elliptical light spots and the flat top beam, which have many applications, can be obtained by selecting certain parameters. The degree of coherence at a point between two orthogonal electric field components, the degree of coherence at a pair of points between two identical electric field components, and the degree of coherence at a pair of points between two orthogonal electric field components of stochastic electromagnetic vortex beams in the focal plane are investigated respectively. It is shown that the topological charges and transverse coherent length of incident vortex beams have very obvious effects on the coherence of focused beams.