High-Transmittance Millimeter-Wave Metasurface Structure Based on Geometric Phase

Unit transmittance is a critical indicator to measure the performance of a metasurface. Based on the geometric phase principle and transmission matrix analysis, a high-transmittance millimeter-wave metasurface structure operating at 120 GHz is designed in this work. The proposed structure is composed of two identical metal layers and a dielectric layer. By adjusting the rotation angle of the metal structure, the phase of the incident 120 GHz circularly-polarized (CP) electromagnetic (EM) wave can be continuously adjusted in the range of 0°-360°. Meanwhile polarization conversion is also realized. Compared with the theoretical efficiency limit of 25% for a single-layer transmissive metallic metasurface, the designed bi-layer metal structure greatly increases the transmittance efficiency of the metasurface to over 90%. Finally, the effectiveness of phase manipulation is verified by applying this structure to generating different modes of high quality orbital angular momentum (OAM) beams.