Polarization-tunable plasmonic coloration across ultrawide gamut using lossy-metal/dielectric/width-modulated lossy-metal subwavelength grating structure

Switchable structural coloration has attracted significant interest in many applications because this approach can dynamically generate static and multiple colors based on external stimuli. However, the dynamic controllable gamut is limited to a narrow visible region. This study experimentally demonstrated polarization-tunable plasmonic color across an ultrawide gamut using lossy-metal/dielectric/width-modulated lossy-metal subwavelength grating (SWG). The numerically simulated electromagnetic field distribution shows that p-polarized (the electric field perpendicular to the grating) and s-polarized (the field parallel to the grating) irradiations excited spectrally broadened optical resonances owing to the optical damping of the lossy metals and these resonances induced a large phase difference between both types of irradiations over a wide wavelength region. Our hypothesis that a suitable combination of different structural SWG widths can be used to design the phase difference was validated via these simulations. Moreover, the calculated field distribution showed that the designed phase difference varied the polarization states of the reflected light across the entire visible region, depending on the wavelength. The SWG structure was fabricated using electron-beam lithography, and the measured reflection spectra exhibited excellent agreement with the simulation results. The fabricated sample formed an ultrawide oval in the CIE1931 color space by rotating the polarizer and realized an extremely wide polarization-tunable gamut compared to the existing gamut. The proposed strategy, which benefits from lossy materials, contributes to development of novel design concepts and material selection for various color-control applications.