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

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

Automated summary

The high efficiency achromatic metalens has diffraction-limited focusing capability at wavelengths ranging from 1000 nm to 1700 nm, comprised of two stacked nanopillar metasurfaces that independently control the required focusing phase and dispersion compensation, achieving a large achromatic bandwidth and high efficiency focusing.