一种设计大数值孔径衍射元件的优化方法

本文以菲涅耳衍射透镜的设计为例，在单位周期内的相位台阶数与最小特征尺寸之间关系的基础上，提出了减小元件边缘单位周期内的台阶数，以增大最小特征尺寸的一种新的设计大数值孔径衍射元件的优化设计方法，并对衍射效率进行了讨论。确定了多台阶衍射透镜优化设计的结构参数。最后给出了设计实例，与深浮雕法和相位匹配法比较，本文法设计的元件仅需套刻3次，而衍射效率的理论值达55.4%，是一种有效的优化方法。

An Optimal Method to Design Diffractive Element with Large Numerical Aperture

Based on the relationship between phase quantized levels in unit period and the smallest feature size of the Fresnel diffractive lens,a new optimal design method for diffractive element with large numerical aperture is proposed and the diffraction efficiency is discussed.The parameters of the multi level diffractive lens are determined.A design example of a Fresnel lens with large numerical aperture is presented,which is compared with the deep etching method and the phase matching method in the diffraction efficiency and in the number of etching.It was shown that the theoretical diffraction efficiency of the designed Fresnel lens is 55.4 % with the etching number of 3,which is competitive with the existing methods.