Dielectric gradient metasurface for efficient terahertz wave focusing

In this paper, we report a dielectric gradient metasurface (DGM) of high transmission with a complete 2π phase control, which allows more efficient terahertz (THz) wave focusing compared to the state-of-the-art plasmonic metasurfaces. The DGM was theoretically and experimentally demonstrated to focus a THz plane wave to a beam spot of several wavelengths, which may have potential for applications in THz imaging and communication systems.