部分相干多离轴涡旋矢量光束的传输特性

Propagation properties of partially coherent vector beam with multiple off-axis vortex phases

基于相干与偏振的统一理论,采用傅里叶变换和卷积定理的方法,研究了携带多个离轴涡旋相位的径向偏振矩形对称余弦-高斯关联结构光束的传输特性.结果表明,该光束因其独特的空间相干结构而具有自分裂特性,可以分裂成4束完全相同的子波瓣.更重要的是,多离轴涡旋相位的调制可以作用在每个子波瓣上.当相干度较大时,通过调制光束的离轴涡旋数量N_(0)和光束阶数可以在焦平面处产生具有三角形或正方形等多边形空心光强分布的光斑阵列,并且每个子波瓣上对应的偏振态呈现倒三角形或斜正方形的椭圆分布.当相干度较小时,部分相干光束的空间相干性调控占主导作用,多离轴涡旋相位的调制效果消失,每个子波瓣的光强退化成高斯形式分布,但其偏振态分布仍保持不变,与光束阶数和相干长度无关.此外,当利用障碍物遮挡住其中一个离轴涡旋相位时,光束仍具有一定的自修复能力.然而,若将其中一个离轴涡旋相位完全遮挡住,此时每个子波瓣的强度分布和偏振态分布都遭到破坏,会出现不同程度的“缺口”.

In this paper,we investigate the propagation properties of radially polarized rectangular-symmetric cosine-Gaussian Schell-model(RCGSM)beam with multiple off-axis vortex phases by using Fourier transform and convolution method based on the unified theory of coherence and polarization.The results indicate that the radially polarized RCGSM beam has self-splitting properties and can be split into four identical lobes due to its unique spatial coherence structure.Furthermore,the modulation of multiple off-axis vortex phases can be acted on each lobe.For high coherence,the spot arrays with triangular or square hollow light intensity distribution can be generated in the focal plane by modulating the number of off-axis vortices(N_(0))and the beam order,and the corresponding state of polarization on each lobe presents an inverted triangular or oblique square elliptic distribution.However,for small coherence,the modulation effect of multiple off-axis vortex phases disappears and the light intensity of each lobe degenerates into a quasi-Gaussian distribution,whereas its state of polarization keeps invariant,which is independent of the beam order and coherence length.In addition,the beam still has a certain self-healing ability for one of the off-axis vortex phases partially blocked by an obstacle,but it will be destroyed for completely blocking,resulting in a notch on each lobe.