Chung Haejun, Miller Owen D
Opt Express. 2020 Mar 2;28(5):6945-6965. doi: 10.1364/OE.385440.
We use inverse design to discover metalens structures that exhibit broadband, achromatic focusing across low, moderate, and high numerical apertures. We show that standard unit-cell approaches cannot achieve high-efficiency high-NA focusing, even at a single frequency, due to the incompleteness of the unit-cell basis, and we provide computational upper bounds on their maximum efficiencies. At low NA, our devices exhibit the highest theoretical efficiencies to date. At high NA-of 0.9 with translation-invariant films and of 0.99 with "freeform" structures-our designs are the first to exhibit achromatic high-NA focusing.
我们采用逆向设计来发现超颖透镜结构，这些结构在低、中、高数值孔径下均呈现宽带、消色差聚焦特性。我们表明，由于晶胞基的不完整性，即使在单一频率下，标准的晶胞方法也无法实现高效的高数值孔径聚焦，并且我们给出了其最大效率的计算上限。在低数值孔径下，我们的器件展现出了迄今为止最高的理论效率。在高数值孔径下——平移不变薄膜的数值孔径为0.9，“自由形式”结构的数值孔径为0.99——我们的设计首次实现了消色差高数值孔径聚焦。
