Paired Metasurfaces for Amplitude and Phase Control of Wavefronts

Gradient metasurfaces that are passive, low-loss, and reflectionless, are generally limited to tailoring the phase of an incident wavefront. Here, we show that by using two phase-discontinuous bianisotropic metasurfaces, the amplitude and phase distributions of an aperture field can be independently controlled. The paired metasurfaces are separated by a distance on the order of a wavelength. Due to the flexibility of the design procedure, an arbitrary incident field can be used as a source to produce a desired complex field pattern. This property makes the method relevant to a variety of applications, including producing custom (shaped and steered)far-field radiation patterns and 3-dimensional holograms.