Compared with traditional color dyes, structural color has the advantages of high resolution and good stability, which can achieve full-tone modulation in the visible light range. All-dielectric metasurface structures are proposed to replace plasmonic metasurfaces with higher losses. Due to the existence of high-order dipole resonance mode in the short-wave range, the enhancement of color saturation is limited. Aiming at this problem, a feasible scheme to suppress high-order dipole mode is proposed.
In a study published in Optics Express, a research group led by Prof. GAO Jinsong from the Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP) of the Chinese Academy of Sciences (CAS) proposed an all-dielectric grating structure color filter with narrow bandwidth and high-quality factor.
Using the finite difference time domain method, researchers conducted an in-depth comparative study on HfO2 gratings and SiO2/HfO2 gratings. In this process, GAO and his group found that the addition of the SiO2 layer effectively suppressed the generation trend of high-order dipole mode and improved the saturation of the structural color. The physical mechanism of the result was explained by the magnetic field distribution and the electric field vector diagram. They then explored the influence of the structural parameters on the spectral curve and the sensitivity of the polarization state.
Based on the above finding, the all-dielectric grating proposed by the researchers ensured that the reflectivity at the peak position is close to 1, and the transmittance at the non-resonant peak position exceeds 99%. The realization chromaticity coordinates occupied most of the area of the CIE-1931 chromaticity diagram. By adjusting the duty cycle, researchers obtained the excellent spectral characteristics with the FWHM =2nm and the quality factor Q=424.5.
This all-dielectric grating has excellent characteristics of high structural color quality, low full width of half maximum and high-quality factor, which is of great significance to the fields of sensing, display imaging and other fields, according to the researchers.
