Structurally reordered crystalline atomic layer-dielectric hybrid metasurfaces for near-unity efficiency in the visible

Abstract

Metasurfaces, consisting of sub-wavelength scale nanostructures, have garnered significant attention as promising alternatives to conventional optical elements. However, traditional metasurfaces are often limited by material inefficiencies, fabrication complexity, and challenges in achieving seamless integration with standard semiconductor equipment. Here, we propose highly efficient crystalline titanium dioxide (TiO₂)-silicon dioxide (SiO₂) hybrid metasurfaces, fabricated using plasma-enhanced atomic layer deposition. By recrystallizing the state of the TiO₂ atomic layer under optimized deposition conditions, we significantly increase the refractive index by 0.43 at a wavelength of 400 nm compared to its minimum value. Our hybrid metasurfaces, constructed by directly etching nanostructures into SiO₂ substrates, substantially enhance cross-polarization transmittance, offering near-unity efficiencies across red (from 1 % to 95 %), green (from 3 % to 95 %), and blue (from 5 % to 75 %) wavelengths. We apply these hybrid metasurfaces to achieve diffraction-limited imaging with large-aperture 5 mm-sized metalenses in each color. This hybrid metasurface paves the way for real-world applications by extending SiO₂—widely used in the industry but previously limited by its low refractive index—into a high-efficiency metasurface material for the visible spectrum.