Fig. 5
From: Recent advancements of metalenses for functional imaging
High-NA metalenses. Optimization-based ultrahigh-NA metalenses: a Schematic of metalens designed using hybrid optimization algorithm. b Side-view SEM image of metalens. c Measured, simulated, and ideal intensity profiles of focal spot. Captured image of focal spot (inset). a-c are reproduced with permission [126] (Copyright 2018, American Chemical Society). d Structures of (left) conventional, (middle) topology-optimized, and (right) topology-optimized fabricable metalens (scale bar = 2 μm). e Simulated focusing efficiency of metalenses. Shaded area shows the region between the efficiency of conventional metalens and vector diffraction theory. (d) and (e) are reproduced with permission [116] (Copyright 2022, Wiley-VCH). Asymmetric-dimer-grating-based ultrahigh-NA metalenses: f Asymmetric dimer array and g side-view SEM image of metalens (scale bar = 500 nm). h Measured normalized intensity distribution on xz-plane. f-h are reproduced with permission [127] (Copyright 2018, American Chemical Society). i Adaptively arranged asymmetric dimers. Blue box shows Fresnel zones of metalens. j Focusing efficiency with different polarization angles. (insets) Point spread function for polarization angles of (left) 30°, (middle) 70°, and (right) 110°. k Three-dimensional image describing focusing performance of metalens. i-k are reproduced with permission [67] (Copyright 2022, Wiley-VCH)