Phase and magnitude constrained metasurface holography at W-band frequencies

Holographic optics are an essential tool for the control of light, generating highly complex and tailored light field distributions that can represent physical objects or abstract information. Conceptually, a hologram is a region of space in which an arbitrary phase shift and amplitude variation are added to an incident reference wave at every spatial location, such that the reference wave will produce a desired field distribution as it scatters from the medium. Practical holograms are composed of materials, however, which have limited properties that constrain the possible field distributions. Here, we show it is possible to produce a hologram with continuous phase distribution and a non-uniform amplitude variation at every point by leveraging resonant metamaterial elements and constraining the hologram's pixels to match the elements' resonant behavior. We demonstrate the viability of the resonant metamaterial approach with a single layer, co-polarized holographic metasurface that produces an image at millimeter wavelengths (92.5 GHz) despite the elements' limited phase range and coupled amplitude dependency.