给出了基于旋转体时域有限差分法的严格的矢量分析模型,应用该模型分析了多个多台阶圆形衍射微透镜的设计实例。研究了设计参量和制作误差对其聚焦性能的影响。结果表明增加环带数,但保持其他设计参量例如焦距、入射波长不变时,焦点场强增大、焦斑变小、焦深变短;只增加台阶数时,聚光作用加强,但台阶数达到8～10后,聚焦效果趋向稳定,因此建议在实际加工中,台阶数选择8～10。用二元掩模板套刻制作多台阶时,容易产生制作误差。设计了在第三次套刻制成8个台阶过程中产生了对准误差和系统刻蚀误差的两类多台阶微透镜。分析结果表明对准误差对多台阶微透镜聚焦效果的影响较大,加工时要尽量避免,而系统刻蚀误差对多台阶微透镜聚焦效果的影响较小。

A rigorous vector analysis model based on body-of-revolution (BOR) finite-difference time-domain (FDTD) method is presented, many design examples of multilevel circular microlens are analyzed by this model, and the influence of design parameters and fabrication error on the focusing performance of the designed microlens is investigated. The results show that the electric field magnitude on focus increases, and the focal radius and focal depth minish when the zone number is increased but other parameters such as focal length and incident wavelength are constant. The focusing effect is intensified when adding step number only, but after the step number adds to 8～10, the focusing effect tends to be stable. It's suggested that the step number is set as 8～10 in actual fabrication. When binary mask is used to lithograph the multilevel, fabrication error is easily generated. Two kinds of multilevel microlens with alignment error or system etching error are designed, which generate the above error in the third etching process of fabricating eight levels. Analysis result shows that the alignment error has passive influence on the focusing effect of multilevel microlens, so it should be avoided in fabrication, but the system etching error has little influence on the focusing effect of multilevel microlens.