Broadband, high-efficiency, arbitrary focusing lens by a holographic dielectric meta-reflectarray

In this paper, a metalens based on the dielectric meta-reflectarray consisting of silicon nanorods in combination with a gold ground plane is proposed to realize an arbitrary focusing lens. We have demonstrated that the meta-reflectarray is served as a half-waveplate with near-unity reflectance and over 98% polarization conversion efficiency over a wavelength range from 1.5 to 1.6 μm for circularly polarized light incidences. We have also demonstrated that single spot and four-spaced spots focusing with more than 96% diffraction efficiency over 100 nm bandwidth can be realized by this metalens in the near infrared band just by controlling the reflection phases. The spatial phase distributions of the corresponding designed metalens can be determined via a computer-generated hologram method. Meanwhile, the desired phase can be simply obtained by modulating the orientation of the silicon nanorods. The proposed approach demonstrates a high-performance solution for creating low-cost and lightweight beam-shaping and beam-focusing devices at telecommunication wavelengths.