Anisotropic Metasurface And Its Applications In Polarization Manipulation

Metamaterials are composed of unit cells which are arranged periodically or non-periodically. They have provided effective ways to manipulate electromagnetic waves by achieving the desired electrical and magnetic characteristics. Metasurfaces as a kind of two-dimensional(2D) Metamaterials have been introduced by applying a seried of metallic structures on the interface to generate discontinuous phase shifts on propagating electromagnetic wave between two media, yielding anomalous reflections and refractions. Based on the metasurface, many interesting works have been present in optical, such as negative refractions, negative reflections, and polarized rotations that the ordinary electromagnetic surface can’t realized. However, the transmission efficiency of metasurface is low make it difficult to meet the requirements of applications in microwave when the reflective metasurfaces can manipulate the reflections of incoming waves with high efficiency, reaching nearly 100%. In this paper, we propose anisotropic reflective metasurfaces in microwave with the capacity to manipulate the different polarization of electromagnetic wave independently. Based on this principle,we design functional devices such as polarization beam splitting and polarization conversion, whose measurement results agree with simulation results verified good capacity of reflective metasurface to control the different polarization independently. The main contributions of these theses are listed below:(1) Polarization conversions have been proposed by using anisotropic metasurface. The first device is designed for dual polarization in dual frequency which is composed of unit cell of I-shaped structures with strong anisotropy. However, we achieved polarization conversion in a narrow band because of the limitations of I-shape. The second device is designed for broadband polarization which is composed of two orthogonal I-shaped structures.(3) Polarization beam splitters have been proposed by using anisotropic metasurface. We show that the metasurface composed of two orthogonal I-shaped structures manipulates the reflective phases of two orthogonal linearly-polarized waves independently by changing the dimensions of I-shaped structure. Hence, the incident wave can be manipulated as desired after reflected by the anisotropic metasurface based on Generalized Snell’s Law. Two polarization beam splitter have been presented to deflect the different polarized waves to the direction in one plane or not.(4) Polarization conversions with deflected wave have been proposed by using metasurface. The polarization converter we have been introduced will cause serious effect by feed, due to the same direction of incident wave and reflected wave. Therefore, we proposed a new polarization converter which the direction of reflected wave can also be designed to improve the performance.