A Dual-polarized High-NA Achromatic Transmission Huygens’ Metalens

In this paper, we present the first dual-polarized achromatic metalens made from a Huygens’ metasurface element. Employing a novel Huygens’ architecture with miniaturized size and improved tuning range, we achieve wideband, linear-phased, highly transmissive elements capable of generating a large range true-time-delay. This allows us to construct a dual-polarized achromatic metalens with a large numerical aperture. As a proof of concept, we design a dual-polarized achromatic metalens for which the focal length is maintained at $6.4\pm 0.15\lambda_{c}$ across the operation band (K-band, 21.5-26 GHz), where $\lambda_{c}=12.5$ mm is the wavelength corresponding to the center frequency of 24 GHz. The simulated focusing efficiency is over 65% across the operation bandwidth. The combination of the miniaturized unit cell and increased tuning range allows this dual-polarized achromatic metasurface to have a numerical aperture of 0.64 – which is the highest known among achromatic metalenses in the microwave region. This metasurface shall find attractive applications in broadband imaging and communication at microwave and mm-wave frequencies.