Fig. 3

Achromatic metalenses for multiple discrete wavelengths. (a) Optical and SEM images of the multisector lens (upper line) and the interleaved lens (lower line) [58]. (b) Intensity measured in the axial plane and in the focal plane at 915 and 1550 nm for the multisector lens (upper line) and the interleaved lens (lower line) [58]. (c) Artist’s view of the three-layer lens. When illuminated with white light, each layer focuses its designated part of the spectrum to a distance of 1 mm along the optical axis [59]. (d) Left panel: Aberration correction of 450 nm, 550 nm and 650 nm. Right upper panel: theoretical calculation of the focal distance for a conventional Fresnel zone plate (FZP) (red line) and the measured focal points at the RGB wavelengths of the conventional FZP (crosses) and metasurface FZP (circles). Right lower panel: demonstration of color imaging using the fabricated metasurface FZP element [59]. (e) A meta-atom composed of a square cross-section amorphous silicon nano-post on a silicon dioxide layer on a metallic reflector. SEM of the fabricated nano-posts and devices [60]. (f) Measured intensity in the axial plane of the metasurface at five wavelengths [60]