Terahertz planar lenses based on plasmonic metasurfaces

Plasmonic planar lenses on silicon substrate are designed to realize terahertz (THz) wave focusing. Super-unit-cells containing eight different resonant units are presented to construct eight concentric rings on the silicon substrate. By controlling of the position distribution of the resonant units, it is shown that focusing at 4.3 THz can be achieved. Moreover, due to that the eight units can steer THz wave and keep phase gradient in frequency range of 4.2 to 4.5 THz, the metalenses can realize broadband THz focusing. The results imply the potential applications in THz wave control devices of light collection and multi-channel optical communication.