Design of high efficiency achromatic metalens with large operation bandwidth using bilayer architecture

Achromatic metalens composed of arrays subwavelength nanostructures with spatially varying geometries is attractive for a number optical applications. However, the limited degree freedom in single layer achromatic metasurface design makes it difficult to simultaneously guarantee sufficient phase dispersion and high diffraction efficiency, which restricts bandwidth efficiency metalens. Here we propose demonstrate diffraction-limited focusing capability at wavelength ranging from 1000 nm 1700 nm. The comprises two stacked nanopillar metasurfaces, by required compensation can be controlled independently. As result, addition large bandwidth, averaged bilayer higher than 64% near-infrared region. Our opens up possibility obtain simultaneously, great significance broadband metasurface-based devices.