Metasurface holograms for visible light

Holography, a revolutionary 3D imaging technique, has been developed for storing and recovering the amplitude and phase of light scattered by objects. Later, single-beam computer-generated phase holography was proposed for restoring the wavefront from a given incidence. However, because the phase modulation depends on the light propagation inside the material, the thickness of phase holograms usually remains comparable to the wavelength. Here we experimentally demonstrate ultra-thin metasurface holograms that operate in the visible range whose thickness is only 30 nm (approximately 1/23 of the operational wavelength). To our knowledge, this is the thinnest hologram that can provide both amplitude and phase modulation in the visible wavelength range, which generates high-resolution low-noise images. Using this technique, not only the phase, but potentially the amplitude of the incident wave can be efficiently controlled, expanding the route to new applications of ultra-thin and surface-confined photonic devices. Holographic techniques provide phase and amplitude information for images of objects, but normally the hologram thickness is comparable to the light wavelength used. Ni et al.present ultra-thin plasmonic holograms that control amplitude and phase in the visible region and are just 30 nm thick.