Electric Field Enhancement in 3-D Tapered Helix Antenna for Terahertz Applications

A tapered helix monopole as a part of a rectenna for the detection of terahertz radiation is proposed. The antenna consists of a truncated conical helix extruded from a planar spiral and in a nanometric metallic whisker connected to one of its edges. The whisker faces a semiconductor substrate constituting the antenna ground plane. The structure is designed to be combined with a rectifying junction, realized just below the whisker base, which produces the direct conversion of terahertz electromagnetic field into dc current. The figure of merit of the structure is the electric field enhancement factor at the metallic whisker/semiconductor interface. Numerical full-wave simulations show that, for the tapered helix monopole, the field enhancement factor value can be higher than 26 000, which is approximately one order of magnitude greater than previously reported values in the literature. Detailed description of the fabrication process and investigation of antenna performances for different values of geometrical parameters are presented.