Subwavelength-Resolution Terahertz Hologram with Arbitrary Curved Trajectory and Customized Polarization Structures

Terahertz holography plays an important role in modern information photonics. However, conventional methods suffer from large pixel sizes due to the wavelength diffraction limit and a complex setup to generate holograms. Thanks to the unprecedented capability of metasurfaces in light control, here a metalens holography is proposed and experimentally demonstrated that can realize a subwavelength-resolution hologram with both an arbitrary curved trajectory and customized polarization structures in the terahertz regime. The all-dielectric multi-foci metalenses, with the combination of geometric and propagation phase approaches, are exploited for fine control of the cross-polarization and co-polarization of the incident circularly polarized beam. By separate manipulation of the two orthogonally polarized wavefronts, the spatial position and polarization state of every focal point can be controlled independently. By using every focal point of the metalens as the pixel unit, the typical terahertz holograms of 2D ring, Archimedes spiral, and 3D knot curved trajectories with various customized polarization structures are performed with good agreement between the experimental and simulations. The meta-holographic sub-wavelength resolution surpasses the wavelength diffraction limitation imposed by conventional holography, holding the promising application for super-resolution terahertz imaging and high-definition communication.