High-Efficient and Polarization-Insensitive Metalens Using Sub-Wavelength Circular Slot Elements

Metallic metasurfaces sandwiched by several dielectric (or air) mediums provide new routes to develop high-performance metalenses in low spectrums. However, the polarization-dependent unit cell design is one of the main challenges toward multi-polarization plasmonic metalenses especially for high transmission efficiency arrays design. In this paper, to overcome this obstacle, an annular slot element-type metallic metasurface is proposed for the design of high efficient metalens in the microwave band. The meta-atom with different layer metal-dielectric-metal hybrid structure is investigated and compared with each other by using full-wave simulations. Besides, transverse magnetic (TM) and transverse electric (TE) mode of unit cell are specifically presented for transmission magnitude, phase distribution and power intensity. In order to fulfill the required phase profile to create metalens simultaneously with high transmission efficiency, four-layer sub-wavelength metallic metasurface with varying outer radius of slot-element is selected. An ultra-thin microwave metalens operating around 9GHz is thus designed and its focusing performances such as focusing power intensity, full-width at half-maximum of its focusing spot and focusing efficiency are also analyzed with full-simulation microwave studio. The studies here on microwave metalens based on proposed meta-atom provide new ways to develop polarization-insensitive high transmission meta-devices in low spectrum.