Terahertz coupling and transmission via sub-wavelength eccentric coaxial aperture

Sub-wavelength coaxial aperture has been demonstrated as a simple technique for coupling terahertz (THz) radiation on a cylindrical metal wire. From the practical point-of-view, the structure of a coaxial aperture may have a misalignment of the inner conductor, which leads to an eccentric coaxial aperture. Making use of finite difference method (FDM) in bipolar coordinate system (BCS) and finite element method (FEM) with consideration of surface plasmons (SPs), we numerically analyze the coupling and transmission properties in sub-wavelength eccentric coaxial aperture. Results show that the distribution of RF fields is affected noticeably by the structural misalignment. When SPs are considered, the eccentric structure has many benefits compared to the concentric structure.