Structural color printing based on plasmonic metasurfaces of perfect light absorption

Abstract

Subwavelength structural color filtering and printing technologies employing plasmonic nanostructures have recently been recognized as an important and beneficial complement to the traditional colorant-based pigmentation. However, the color saturation, brightness and incident angle tolerance of structural color printing need to be improved to meet the application requirement. Here we demonstrate a structural color printing method based on plasmonic metasurfaces of perfect light absorption to improve color performances such as saturation and brightness. Thin-layer perfect absorbers with periodic hole arrays are designed at visible frequencies and the absorption peaks are tuned by simply adjusting the hole size and periodicity. Near perfect light absorption with high quality factors are obtained to realize high-resolution, angle-insensitive plasmonic color printing with high color saturation and brightness. Moreover, the fabricated metasurfaces can be protected with a protective coating for ambient use without degrading performances. The demonstrated structural color printing platform offers great potential for applications ranging from security marking to information storage.

Figure 1. Plasmonic metasurfaces fabricated on silver-silica-silver three layer structures.

(a) Schematic view of four unit cells for triangular-lattice circular hole arrays fabricated on the silver-silica-silver three layer structure. (b) An example of SEM cross-section image of the metasurface structure with period (P) of 320 nm and hole radius (r) of 100 nm. (c–e) SEM images of three metasurfaces with different lattice geometrical parameters (c: P = 130 nm, r = 35 nm; d: P = 200 nm, r = 50 nm; e: P = 260 nm, r = 65 nm). Insets: Optical reflection microscopy images of the entire 20 × 20 μm² circular hole arrays of triangular lattice. Scale bars: 500 nm.

Figure 2. Analysis of reflection spectra and structural colors for the fabricated plasmonic metasurfaces.

(a) Measured (red solid curves) and simulated (black dashed curves) optical reflection spectra of the metasurfaces with period P = 200 nm and hole radius r = 45 −75 nm (from top to bottom). Insets: The measured optical images of the fabricated 20 × 20 μm² metasurfaces. (b) Measured (red solid curves) and simulated (black dashed curves) optical reflection spectra of the metasurfaces with period P = 130 −260 nm and hole radius r = 30 −60 nm (from top to bottom). Insets: The measured optical images of the fabricated 20 × 20 μm² metasurfaces. (c) CIE 1931 chromaticity coordinates of measured (solid dots) and calculated (hollow dots) optical reflection spectra shown in panel (a). (d) CIE 1931 chromaticity coordinates for optical reflection spectra shown in panel (b).

Figure 3. The demonstrated high-resolution plasmonic color printing with high brightness and saturation.

(a) The original athletics mark image adapted with permission from The Curators of the University of Missouri. (b) SEM image of the fabricated pattern containing six different triangular lattices and corresponding colors shown in panel e. (c) SEM image of the area outlined in panel f. (d) Optical microscopy image of a plasmonic reproduction of the original mark image shown in panel e, containing only yellow and green colors. (e) Optical microscopy image of the plasmonic print presenting another four distinct colors (symbol ‘&’: orange, character ‘S, T’: magenta, pickaxe shape: cyan and word ‘MISSOURI’: navy blue) besides two original colors shown in panel d. Scale bars: 10 μm (b, d and e); 2 μm (c).

Figure 4. Comparison of reflection spectra and structural color for plasmonic metasurfaces without and with the protective polymer coating.

Measured (a,b) and simulated (c,d) optical reflectance spectra of three selected metasurfaces without (a,c) and with (b,d) PMMA coating. (e) CIE 1931 chromaticity coordinates of uncoated metasurfaces. (f) Chromaticity coordinates of the three PMMA-coated metasurfaces. (g) Cross-section of the time-averaged magnetic field intensity (colored contours) and electric displacement (black arrows) distributions for the uncoated metasurface at the wavelength λ₁ indicated in panel c. (h) Magnetic field intensity (colored contours) and electric displacement (black arrows) distributions for the PMMA-coated metasurface at the wavelength λ₂ indicated in panel d.

Figure 5. Color palette and reproduction of an artwork without and with the protective polymer coating.

(a) The measured bright-field microscope images of uncoated metasurfaces with period varying from 120 to 320 nm and hole radius ranging from 25 to 115 nm. (b) The measured bright-field microscope images of the PMMA-coated metasurfaces. (c) Original image of a selected pastel painting obtained from a public domain resource. (d) Optical microscopy image of the uncoated plasmonic painting. Each colored area is visually uniform and exhibits bright color with high contrast, illustrating a high degree of accuracy in the fabrication process. (e) Optical microscopy image of the PMMA-coated plasmonic painting. The influence of spectral redshift induced by the PMMA coating is taken into account by choosing appropriate lattice period and hole radius, so that each color in the original painting is reproduced with high fidelity in the plasmonic painting. Scale bars: 10 μm.