Resonant metasurface with tunable asymmetric reflection

Suppression of backscattered electromagnetic waves by carefully designed structures is highly demanded in a range of applications, some of which are radar invisibility, antenna isolation, and many others. Salisbury screens, composed of a mirror with an additional layer on top, are traditionally used for these purposes. Here, we report on the design and experimental demonstration of a reciprocal screen, which demonstrates asymmetric reflection properties when illuminated from opposite directions. The structure utilizes near-field magneto-electric coupling between subwave-length split ring resonators and wires, forming a metasurface. While the reciprocal structure demonstrates perfect symmetry in transmission, strong backscattered asymmetry is shown to be controllable by carefully choosing the Ohmic losses, which are implemented with lumped resistors soldered into the resonators. Depending on the load, the meta-screen demonstrates switching properties that vary between fully symmetric and completely asymmetric reflection between the forward and backward directions of incident illumination. The frequency selective surface acts as a Huygens element when illuminated from one side and as a perfect mirror when illuminated from the other. The ability to tailor the asymmetric reflectance of electromagnetic metasurfaces by controlling Ohmic losses allows employing additional degrees of freedom in designing of radomes and other antenna devices. Furthermore, the concept could be extended to optical frequencies, where resistive losses can be controlled via direct carrier injection into semiconductor devices. Published by AIP Publishing.