平顶高斯光束通过光阑透镜的焦移

Focal shifts of flattened Gaussian beams passing through an aperture lens

从Collins公式出发 ,研究了平顶高斯光束通过光阑透镜的焦移 ,并用大量数值计算例予以说明。研究表明 ,截断平顶高斯光束的焦移不但由光束的阶数N、光束菲涅耳Fw 决定 ,还与孔径菲涅耳数Fa 有关。与无光阑情形比较 ,对于光阑透镜 ,即使在Fw 很大的情况下 ,仍然存在焦移。

Starting from the Collins formula,focal shifts of flattened Gaussian beams (FGBs) passing through an aperture lens are studied and illustrated with detailed numerical examples. It is shown that focal shifts of apertured FGBs not only depend on the beam order N ,Fresnel number F w associated with the beam,but also depend on the Fresnel number F a associated with the aperture. In comparison with the unapertured case,there still exist focal shifts even for the case of the large Fresnel number F w .