Antireflection High-Index Metasurfaces Combining Mie and Fabry-Pérot Resonances

Minimizing reflection losses is required for the efficient operation of a wide range of optical components. Antireflection coatings supporting Fabry-Pérot resonances are commonly used to solve this problem and can be applied on an industrial scale. Recent work has shown that reflections can also be reduced by placing an array of high-index nanostructures on a surface. In such coatings, antireflection is achieved by tailoring the scattering by optical Mie resonances. Here, we design and fabricate Si metasurfaces that combine both Fabry-Pérot and Mie resonances in a single metasurface to realize a multiresonant broadband antireflection response. We optically characterize the metasurfaces demonstrating 4.1% AM1.5-averaged reflectance across the visible spectrum (425-900 nm). Our metasurface design strategy is generally applicable to different materials and frequency ranges, making our approach relevant for a broad variety of applications.