All-Dielectric Gratings with High-Quality Structural Colors.

We present a dual-layer hafnium dioxide (HfO) grating capable of full-color modulation in the visible spectrum by leveraging the magnetic dipole resonance induced by the lower-layer HfO grating, while the upper-layer HfO grating serves as a refractive index matching layer to effectively suppress high-order Mie resonances at shorter wavelengths. The HfO/HfO grating exhibits a significantly larger distribution area in the CIE 1931 chromaticity diagram compared to the HfO grating. Furthermore, the structural color saturation closely approximates that of monochromatic light. Under varying background refractive index environments, this structure consistently exhibits high-quality structural color. However, the hue of the structural color undergoes alterations. When the polarization angle is below 20°, the saturation of the acquired structural color remains remarkably consistent. However, exceeding 20° results in a significant degradation in the quality of the structural color. This study demonstrates the promising potential for diverse applications, encompassing fields such as imaging and displays.