Fig. 1. Structural diagram of dual-band antireflection coating. (a) Unit cell; (b) planar structure of first layer of gold-polyimide; (c) planar structure of second layer of gold-polyimide

Fig. 2. Reflectivity and transmissivity for dual-band antireflection coating and bare silicon

Fig. 3. Reflectivity for three structures

Fig. 4. Electric field distributions on metal surfaces of different metamaterial structures at different frequencies. (a) Two layer of metal-polyimide structure, 0.471 THz; (b) two layer of metal-polyimide structure, 1.560 THz; (c) SRRs-polyimide structure, 1.560 THz; (d) rectangle-polyimide structure, 1.560 THz

Fig. 5. Reflectivity and bandwidth versus h1. (a) Reflectivity versus h1 at frequency near 0.471 THz; (b) reflectivity versus h1 at frequency near 1.560 THz; (c) bandwidth versus h1 at frequency near 0.471 THz; (d) bandwidth versus h1 at frequency near 1.560 THz

Fig. 6. Reflectivity and bandwidth versus b. (a) Reflectivity versus b at frequency near 0.471 THZ; (b) reflectivity versus b at frequency near 1.560 THz; (c) bandwidth versus b at frequency near 0.471 THz; (d) bandwidth versus b at frequency near 1.560 THz

Fig. 7. Reflectivity and bandwidth versus c. (a) Reflectivity versus c at frequency near 0.471 THz; (b) reflectivity versus c at frequency near 1.560 THz; (c) bandwidth versus c at frequency near 0.471 THz; (d) bandwidth versus c at frequency near 1.560 THz

Fig. 8. Reflectivity of different structures and relationship between reflectivity near different frequencies and rectangular side length b. (a) Reflectivity of two structures; (b) relationship between reflectivity versus b at frequency near 0.813 THz; (c) relationship between reflectivity versus b at frequency near 1.617 THz