Design of Huygens' Metasurfaces for Refraction and Focusing

The systematic design of unit cells for Huygens' metasurfaces is presented here. The Huygens' metasurface implements collocated electromagnetic boundary conditions enforcing the electric and magnetic surface currents of the equivalence principle. This provides the flexibility necessary for efficient interfacial beamforming applications. Furthermore, the boundary condition nature permits achieving this in an electromagnetically thin profile. This concept and its design procedure are verified through application to refraction and Gaussian-beam to Gaussian-beam focusing. The Huygens' metasurfaces presented herein are printed on two bonded boards instead of many stacked, interspaced layers, and can be manufactured using standard PCB fabrication techniques. This simplifies the fabrication, and allows the design to be scaled to higher frequencies. These two bonded boards implement a single, collocated, sub-wavelength array of electric and magnetic dipoles. Furthermore, in contrast to traditional frequency-selective surfaces and transmitarrays, which are on the order of a wavelength thick, these designs are only a tenth of a wavelength thick.M.A.S