部分相干光束的聚焦特性

基于部分相干光的传输方程,研究了光强为高斯分布、空间相干度函数为零阶贝塞耳函数的部分相干光束的聚焦特性。研究结果表明,在几何焦点附近的光强分布不仅依赖于入射的部分相干光束的光强分布,而且还依赖于部分相干光束的空间相干度。当空间相干长度、焦距等参数取某些特定值时几何焦点附近的光强分布将出现平顶光束的分布形式;另外,当空间相干长度取值改变时几何焦点附近的光强分布将出现局域空心光束的分布形式。基于此,可以通过改变部分相干光束的空间相干度来实现对几何焦点附近光强分布的控制,从而获得需要的光强分布。

Focusing Properties of the Partially Coherent Beams

Based on the propagation equation of partially coherent beams,focusing properties of the partially coherent beams,whose intensity distribution is Gaussian-mode and spatial coherence function is Bessel function of zero order,have been investigated.The research results show that the intensity distribution in the neighborhood of the geometrical focus is not only dependent on the intensity distribution of the incident partially coherent beam,but also on its spatial coherence.When parameters of spatial coherence,focal distance etc.are chosen as some specific values,the intensity distribution near geometrical focus or in the focal plane is a flattened intensity profile.On the other hand,if spatial coherence is chosen as other values,bottle beams will take place near the geometrical focus.Based on this,spectral degree of coherence of the incident beams can be modulated to change the three-dimensional(3D) intensity distribution in the neighborhood of the geometrical focus.Finally,an adjustable 3D dark focus is obtained.