Transmissive terahertz metalens with full phase control based on a dielectric metasurface

In this paper, we report a transmissive terahertz (THz) metalens based on a dielectric metasurface that consists of periodically arranged sub-wavelength silicon cross resonators with a spatially hyperboloidal phase profile. By varying arm lengths of the cross resonators, we obtained a full 2π phase coverage with high transmission at target frequency. The fabricated metalens was experimentally demonstrated to focus a continuous THz beam to a spot with a full width at half-maximum of 630 μm at a focal length of 28 mm, which agrees well with the theoretical calculation. This device has potential for applications in THz imaging and communications, and our work can also easily be extended in the design of other planar THz components, such as beam deflectors or vortex plates.