Fig. 1. Schematic of conical open-mouth probe structure

Fig. 2. Power density distribution diagrams of terahertz probe with tip radius of 0.2 mm. (a) In x-z plane; (b) in y-z plane

Fig. 3. Focusing effects of terahertz probe with tip radius of 0.2 mm. (a) Linear power density distribution of probe in z direction at 0.1 THz; (b) linear power density distribution of probe in x direction at z=50 mm at 0.1 THz; (c) single peak structure fitted based on bimodal structure in Fig. 3(b); (d) linear power density distribution of probe at z=50 mm at 0.2 THz

Fig. 4. Power density distribution diagrams of terahertz probe with tip radius of 1 μm. (a) In y-z plane; (b) in x-z plane

Fig. 5. Simulation results of terahertz probe with tip radius of 0.4 mm. (a) Power density distribution in x-z plane; (b) power density distribution in y-z plane; (c) linear power density distribution of probe in z direction; (d) linear power density distribution of probe in x direction at z=50 mm

Fig. 6. Two dimensional near-field scanning imaging system. (a) Schematic of system principle; (b) physical drawing of system

Fig. 7. Probe imaging of resolution plate and sample. (a) Slit imaging with width of 2.0 mm; (b) slit imaging with width of 1.5 mm; (c) imaging of “nk” sample