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Chung, Haejun; Miller, Owen D
Optics express, 2020-Mar-02, 2020-03-02, 20200302, Letnik: 28, Številka: 5Journal Article
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.
