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.

中文翻译：

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通过逆向设计实现高NA消色差金属感

我们使用逆设计来发现在低，中和高数值孔径上表现出宽带，消色差聚焦的金属结构。我们显示出标准的单元格方法由于单元格基础的不完整，即使在单个频率下也无法实现高效的高NA聚焦，并且我们为其最大效率提供了计算上限。在低NA下，我们的设备迄今为止具有最高的理论效率。在高NA下（平移不变胶片为0.9，在“自由形式”结构下为0.99），我们的设计率先表现出消色差高NA聚焦。