Ultrathin Single-Substrate Pancharatnam–Berry Phase Metasurface With High Transmission Efficiency

The Pancharatnam–Berry (PB) phase or geometric phase metasurfaces have been extensively investigated in order to achieve flexible manipulation of circularly polarized (CP) electromagnetic waves. Typically, the thickness or structural complexity of the transmission-type PB metasurfaces may limit their efficiency. Here, we propose a single-substrate, ultrathin, transmission-type PB phase metasurface with a transmission coefficient of approximately unity for CP waves. To achieve this, the Huygens principle is applied in the design. The proposed metasurface is capable of achieving high-efficiency transmission amplitude of two orthogonal linear polarizations in the working frequency band, as well as the 180° phase difference. Thus, high-efficiency CP transmission with nearly unity can be obtained, and 360° of phase modulation can be covered by rotating the element. Meanwhile, the proposed metasurface is a single-substrate structure and its thickness is only $0.06\lambda _{0}$ , offering a simple yet efficient method for antenna design. As a proof of concept, a metalens antenna and an orbital angular momentum (OAM) wave generator based on the proposed metasurface are experimentally demonstrated. The measured results show good agreements with the full-wave simulations, successfully verifying the design theory. The proposed metasurface offers an alternative platform for designing high-performance devices with the advantages of lightweight, low cost, and simple fabrication.