Nonreciprocal Control of Electromagnetic Polarizations Applying Active Metasurfaces

The electromagnetic (EM) controls of spatial nonreciprocal performance have gained much attention due to the extreme attraction of the unusual physical phenomenon. Especially, the emergence of metasurfaces, has enormously promoted the design of manipulating the spatial wave and field to achieve various EM functions. Herein is proposed a method to realize the spatial nonreciprocal manipulation for the EM polarizations using an active metasurface which elaborately integrates the elements of power amplifiers. The proposed nonreciprocal metasurface can have the distinct transmission appearance of EM polarizations. When the spatial wave impinges on metasurface with vertical polarization from one side, the transmitted wave has the same polarization; however, when the spatial wave with vertical polarization is incident from the opposite side, the polarization of the transmitted wave will be converted to horizontal. This novel performance is realized by using the meta-atoms composed of three cascaded components: receiving component, nonreciprocal guiding system, and transmitting component. A prototype of the active metasurface is fabricated and measured, and good agreement is observed between the simulation and measurement results.