Fig. 5

Elimination of monochromatic aberrations within metalenses. (a) Principles and schemes of aberration elimination. Ray tracing plot for a plano-convex refractive lens, flat lens, and an aplanatic metasurface. The yellow-shaded areas represent the dielectric substrate (n = 3.5) and the green lines represent the metasurfaces. The parallel illumination forms an angle α = 10° with respect to the optical axis, NA = 0.5 [65]. (b) Upper panel: schematic of the dielectric metasurface used to implement the metasurface doublet lens. Lower panel: schematic of on-axis and off-axis focusing by the doublet lens corrected for monochromatic aberrations. Right panel: Simulated and measured focal plane intensity profiles for different incident angles [66]. (c) Image taken from the metasurface doublet lens (upper panel) and spherical-aberration-free metasurface singlet lens (lower panel). Scale bar, 100 mm [66]. Insets: zoomed-in details of the images at the locations corresponding to viewing angles of 0 °, 15° and 30°. (d) Schematic of the meta-lens doublet and focusing metalens with different rotation angles [67]. (e) Upper row: focal spot intensity profiles at 0°, 6°, 12°, 18° and 25° incidence angle. Scale bar: 1.1 μm. Lower row: images corresponding to the angle mentioned above [67]. (f) Schematic of the design of flat lenses and axicons [46]. (g) Left panel: phase shifts and scattering amplitude sin cross-polarization for the eight elements used in our metasurfaces. Right panel: theoretical calculations and experimental results of the intensity distribution in the focal region [46]