A space-time holographic metasurface antenna

Holography is a revolutionary imaging technology capable of storing and recovering full-wave information of the light fields scattered by objects. However, current hologram configurations are based on space-only modulation and can merely record the amplitude and phase information of object lights. Here, we advance the holography concept by transitioning it from a space-only, homodyne, and single-tone approach to a spatiotemporal, heterodyne, and multifrequency methodology. We theoretically propose and experimentally demonstrate a space-time holographic metasurface antenna (HMA) capable of encoding and reconstructing the full amplitude, phase, and frequency contents of object waves. We demonstrate the HMA for frequency conversion and holographic beamforming in the far field, as well as multifrequency two-dimensional (2D) and 3D holographic imaging in the near field. The proposed integrative and multifunctional space-time HMA goes beyond the existing holography technology, with the potential to enable a plethora of applications such as augmented/virtual reality, data storage, metrology, and wireless communications.