Design of a polarization-multiplexed, high-resolution, near-field focusing metasurface lens

To meet the requirements of integrated and high-resolution focusing devices for passive millimeter-wave (PMMW) imaging systems, a polarization-multiplexed high-resolution near-field focusing metasurface lens is proposed. Metasurface units consist of two dielectric layers and three metal layers and are designed with a multiarm windmill structure. This design allows the units to independently control the electromagnetic response of incident x -polarized and y -polarized waves while maintaining a thickness of only 0.16 λ (2 mm). The metasurface lens that can achieve dual-channel near-field focusing was designed by combining the focusing principle of the metasurface lens and phase superposition principle based on the above design. The lens consists of 30×30 units and has a size of 120×120mm 2 . According to the simulation results, the lens is able to focus the y -polarized waves of 24 GHz at z =50mm plane with a focal spot size of 0.68 λ (8.5 mm), and the focusing beam efficiency is 35.2%. Similarly, the x -polarized waves of 24 GHz are focused at z =70mm plane with a focal spot size of 0.72 λ (9 mm), and the focusing beam efficiency is 40.7%. The proposed metasurface lens is promising for applications in PMMW imaging systems, medical sensors, automotive millimeter-wave radar, and other related fields, owing to the characteristics of high resolution, compact size, and multifunctionality.