Design and application of high polarized purity metasurface lens

Abstract

Dealing with potential applications of metasurface in lens technologies, we propose a focusing metasurface with high polarized purity based on anisotropic elements, and then put it into application of high gain antenna with high polarized purity. Firstly, we design a metasurface cell with the polarization filtering characteristic, which is capable of transmitting the x-polarized waves efficiently while reflecting the y-polarized waves completely. By changing the metallic patch size, we can modulate the phase shift for the x-polarized transmitting waves. Then by imposing a hyperboloidal phase profile onto the surface, we design a metasurface lens with 105 mm105 mm in size, 2121 in cell number, and 30 mm in focal length. According to the principle of reversibility of light path, the spherical waves emitted from the patch antenna can be converted into plane waves by the focusing metasurface lens, which is used to improve the antenna gain. As for the experiment, we tend to obtain the metasurface lens impinged by differently polarized waves in order to study the lens response to differently polarized waves. The results show that the metasurface acts as a lens when impinged by the x-polarized waves but serves as a reflector when illuminated by the y-polarized waves. That is to say, the y-polarized waves are mostly filtered out while the x-polarized waves are efficiently transmitted and focused, which is in good accordance with the designed principle. Assuming that a patch antenna emits the x/y-polarized waves at the focal point, we obtain not only the antenna gain improved remarkably but also polarized isolation above 25 dB in the operating bandwidth of the designed metasurface. The results of the antenna application give a further proof of the designed lens which eventually contributes to the high gain and high polarized purity of the lens antenna.