Fig. 4

Achromatic metalenses for relatively broadband wavelengths. (a) Optical image of fabricated achromatic converging metalens. Inset: the SEM image of meta-elements [61]. (b) Left panel: measured and simulated focal length of metalens with various NA values. Right panel: experimental (upper row) and numerical (lower row) intensity profiles of achromatic metalens along axial planes at various incident wavelengths [61]. (c) Optical image of fabricated achromatic metalens. Inset: SEM image of meta-elements [62]. (d) Left upper panel: simulated numerical results. Left lower panel: calculated results treating each nanorod as a dipolar source radiating from the surface. Right panel: Numerical (upper row) and experimental (lower row) intensity in the axial plane at six wavelengths [62]. (e) Optical micrographs of the fabricated lens in the infrared wavelength regime [63]. (f) Top panel: height profile of metalens with focal length of 19 mm and the simulated point-spread functions at the design wavelengths. Lower panel: height profile of metalens with focal length of 8 mm and the simulated point-spread functions at the design wavelengths [63]