Figure 36:

Structural color printing with pixels of tunable brightness. (a) Measured reflectance spectra of green-color Ag nanorod pixel arrays, where the luminance decreases with the increase of lattice spacing along the rod’s long axis (P _y ). Insets: associated bright-field microscope images of different samples. (b) Measured reflection spectra (upper panel) and corresponding false-colored SEM images (lower panel) of the mixed nanorod arrays. (c) Optical bright-field image of a fabricated sample showing two colorful parrots. The sample consists of nanorod arrays with tunable brightness and chromaticity. The illumination light is linearly polarized along the rod’s long axis (as the arrow indicates). The fabricated sample is 240 × 312 μm in size, and its square pixel has a side length of 1.28 μm. Modified with permission [342]. Copyright 2020, American Chemical Society. (d) Upper panel: SEM image of a fabricated sample consisting of TiO₂ nanopillars. A super-cell is enclosed by white dashed lines and the false coloring of nanopillars indicates the primary colors that are generated by the respective nanopillars. Scale bar: 500 nm. Lower panel: Calculated transmission spectra corresponding to red (red curves), green (green curves), and blue (blue curves) colors when the nanopillar orientation angle varies from 45° (solid lines) to 30° (dashed lines) and 15° (dotted lines). (e) Illustration of the experimental setup for full-color printing, where a linear polarizer is placed behind the metasurface to decode the generated colors. (f) Reproduction of the painting “girl with a pearl earring”. Scale bar: 50 μm. Modified with permission [244]. Copyright 2020, Optica Publishing Group.