Fig. 1

High focusing efficiencies of metalenses. (a) Schematic of the metal-dielectric-metal (gold-glass-gold) meta-element with fixed parameters Λ = 240 nm, ts = 50 nm, and t = 50 nm. The normally incident wave with wavelength of 800 nm is x-polarized. Top panel: SEM image (bar length is 1 μm) of the period array of gold nanobricks. Middle panel: a magnification SEM image of the structure. Bottom panel: the designed geometry [50]. (b) Focusing efficiency and intensity enhancement [50]. (c) Schematic of the aperiodic high-contrast transmitarrays and optical microscope image. Scale bar, 100 mm. Right penal: SEM images of the silicon posts [51]. Scale bars, 1 μm. (d) Focus FWHM spot size, transmission and focusing efficiency of the micro-lenses for devices with different focusing distances [51]. (e) Optical image of the metalens designed at the wavelength of 660 nm. Scale bar, 40 mm. SEM micrograph of the metalens [52]. Scale bar, 300 nm. (f) Measured focusing efficiency at wavelength of 660 nm and 532 nm and intensity distribution in dB of the x-z plane [52]. (g) Left panel: SEM image of the 10 × 10 metalens array. Diameter of each metalens is 30 μm. Right panel: SEM image of a single metalens [53]. Scale bar: 5 μm. (h) Measured focusing efficiency and intensity enhancement of the broadband metalens and chromatic metalens [53]