Fig. 1. Structure diagrams and parameters of stereo metallic pillar: (a) Three-dimensional diagram of unit cell; (b) dispersion relation for the fundamental mode in the first Brillouin zone; (c) effective index n_eff at 0.75 THz with the lateral width a

Fig. 2. Scheme and characteristics of on-chip lens based on gradient index: (a) Structure diagram and simulation result; (b) the electric-field E_z distribution in xy and xz cross-section; (c) the normalized electric-field amplitude along the y direction at the focus

Fig. 3. Schematic diagram and characteristics of planar telescope: (a) Schematic diagram; (b) the electric-field E_z distribution in xy cross-section; (c) the normalized electric-field amplitude along the y direction at the three dashed line position

Fig. 4. Schematic diagram and characteristics with oblique incidence of planar telescope. (a) Schematic diagram; (b) the electric-field E_z distribution in xy cross-section

Fig. 5. Schematic diagram and characteristics of waveguide coupler. (a) Schematic diagram; (b) the electric-field E_z distribution in xy cross-section; (c) the normalized electric-field amplitude along the x direction on the propagation path of y=0

Fig. 6. Schematic diagram and characteristics with two oblique incidence of waveguide coupler. (a) Schematic diagram; (b) the electric-field E_z distribution in xy cross-section

Fig. 7. Schematic diagram of dual-function lenses

Fig. 8. Characteristics of dual-function lenses. (a) Luneburg lens; (b) Fisheye lens

Fig. 9. Fabrication process flow chart of functional devices based on metallic pillars