Fig. 6

Spectral- and spatial-multiplexed metasurface. a Enhanced optical security provided by a six-color holographic color print. Luigi Russolo’s painting Perfume can be reconstructed under incoherent broadband illumination. Optical micrographs of pillar arrays that produce the colors used in the print are shown on the right panel. Three independent holographic images can be obtained by illuminating with 638 nm red, 527 nm green, and 449 nm blue lasers, respectively [87]. b Schematic illustration of the all-dielectric metasurface that integrates dual working modes for incoherent color printing and far-field holography by modulating spatial and spectral responses simultaneously. Selected two types of meta-atoms and their calculated structural colors in the CIE 1931 chromaticity diagram are shown on the top panel [88]. c Metasurface for sub-micron resolution HSB color printing and full-color hologram integration. The RGB unit consisting of multiplexed c-silicon nanoblocks for HSB colour tuning is shown on the right top corner [89]. d Schematic of the 3D-integrated metasurfaces composed of vertically stacking a color-filter microarray with a hologram for achieving full-color holography [90]