Fig. 1. Color performance of the proposed bilayer anisotropic metasurfaces. (a) Schematic of the color pixel consisting of a 110 nm thick PMMA film patterned by arrays of elliptical-shaped holes clamped by two aluminum (Al) metallic thin films. The ratio of the major axis to the minor axis is rab=2a/2b. (b) Cross-polarized reflection spectra of anisotropic metasurfaces with different minor diameters from 165 nm to 275 nm with 10 nm step. The period is 440 nm, the raP is 0.625, and the major diameter is 275 nm. Inset: normalized reflection spectra at resonant wavelengths as a function of the minor axis. (c) Electric field distributions |Ey| of the resonant peak 1 at 516 nm and peak 2 at 504 nm wavelength in (b). (d) Cross-polarized reflection spectra of anisotropic metasurfaces with different periods from 380 nm to 600 nm with 20 nm step. raP is 0.6 and rab is 1.15. The insets are the corresponding structural colors.

Fig. 2. (a) Calculated zeroth-order co-polarized reflection spectra and (b) total reflection spectra of the metasurface with the period of 400 nm. For each case, rab increases from 1.2 to 1.5. The insets are the corresponding structural colors. (c) Co-polarized reflection spectra of anisotropic metasurfaces with different periods from 380 nm to 600 nm with 20 nm step. raP is 0.6 and rab is 1.15. The insets are the corresponding structural colors.

Fig. 3. The brightness control of structural color. (a) Bright field microscope image of color palette composed of elliptical-shaped hole arrays with the rab from 1.2 to 1.7 and the period from 380 nm to 620 nm. The raP is 0.84. (b) Corresponding CIE 1931 chromaticity diagram of (a) with the periods from 380 to 620 nm. (c) Calculated (first column) and measured (second column) zeroth-order cross-polarized reflection spectra of the metasurface with different periods of 400, 500, and 580 nm. For each case, rab increases from 1.2 to 1.5. SEM images (third column) of nanohole arrays of (c) with rab of 1.2 and 1.5, respectively. The scale bar is 200 nm. (d) Corresponding brightness in 3D HSB color space of the measured reflection spectra in (c). The position in the HSB space is gradually rising along the outermost layer of the cone.

Fig. 4. Optical performance of the “hue circle” under 5× magnification. (a) Optical microscope image of “hue circle” and the corresponding SEM images. The period is 380 nm, 390 nm, 420 nm, 430 nm, 450 nm, 460 nm, 480 nm, 500 nm, 520 nm, 580 nm, 600 nm, and 620 nm, respectively. (b) Measured and calculated cross-polarized reflection spectra. (c) International Commission on Illumination (CIE) 1931 chromaticity diagram calculated by the measured and calculated cross-polarized reflection spectra.

Fig. 5. Demonstration of HSB printed image and resolution. (a) HS and HSB images of the designed windmill. (b) Optical image and SEM image. The optical images are measured with a 5×/0.15 objective. Inset: SEM image of the blue box in the optical microscope image at 10,000× magnification (first row) and 30,000× magnification (second row). The scale bars are 1 μm and 200 nm, respectively. (c) Optical microscope images of the resolution pattern with sub-pixel sizes of 20, 10, 5, 4, 3, 2, and 1.2 μm, which covers the resolution required by most application scenarios.