Wide-gamut Saturated Structural Colours Based on Colour Filters

Abstract

We demonstrate a multipolar modulation strategy for high-purity structural colors using all-dielectric metasurfaces. Periodic hollow nanocylinders are constructed on an MgF2 substrate. The metasurface achieves ultra-narrowband and high-efficiency reflection in the visible spectrum. The designed nanostructure consists of coaxially stacked MgF2, TiO2, and a-Si layers. The introduction of the high-index dielectric layer provides additional control over the multipolar interactions and modifies the radiation pathways of the resonant modes. Precise control of the nanocylinder diameter D produces narrowband reflection spectra from 450 nm to 650 nm. The FWHM remains below 9 nm. The peak reflection efficiency exceeds 98%. Blue, green, and red channels are obtained at D = 180 nm, 220 nm, and 290 nm, respectively. The spectral response originates from the dominant excitation of magnetic dipole resonances together with multipolar interference regulation. Optical impedance engineering across the multilayer configuration plays a key role. Parasitic multipolar scattering at nonresonant wavelengths is strongly suppressed. The reflection spectrum thus shows enhanced monochromaticity and purity. This strategy delivers color saturation exceeding 93%. It enables continuous and complete hue coverage. The color gamut expands to 217.2% sRGB and 140.4% Adobe RGB. This study provides a new design paradigm for ultra-high-saturation displays. It also benefits precision, narrowband optical filtering, and biomimetic intelligent optical interfaces. In addition, it offers important physical insights into nanophotonic structures governed by multipolar resonance control.