Fig. 1. Diagram of terahertz photoconductive antenna device

Fig. 2. Schematic diagram of electric field around a spherical metal nanoparticle

Fig. 3. Rectangular, cylindrical, and hexagonal prism micro-nano structures

Fig. 4. Upper cylindrical micro-nano structure arranged by 3×4 equilateral triangles

Fig. 5. Selected upper cylindrical micro-nano structure electric field intensity diagram

Fig. 6. Selected upper cylindrical micro-nano structure transmittance diagram

Fig. 7. First double-layer cylindrical micro-nano structure diagram

Fig. 8. Electric field intensity diagram of the first double-layer cylindrical micro-nano structure

Fig. 9. Double-layer heterogeneous micro-nano structure diagram

Fig. 10. Electric field intensity diagram of double-layer heterogeneous micro-nano structure

Fig. 11. Transmittance diagram of double-layer heterogeneous micro-nano structure