Fig. 1. The schematic diagram of the unit in our calculation structure.

Fig. 2. The extinction spectrum (a) and CD spectrum (b) of our proposed structure with l = 560 nm and w = 400 nm, respectively. The EM field intensity distributions for Ag hole array structure with air at λ = 560 nm (c) and 582 nm (d), respectively. The insert plot is the extinction spectrum with the air filled in the hole.

Fig. 3. The extinction spectra (a) and CD spectra (b) of our proposed structure with w = 400 nm and l = 520 nm, 560 nm, 600 nm, and 640 nm, respectively.

Fig. 4. The extinction spectra (a) and CD spectra (b) of our proposed structure with l = 560 nm and w = 360 nm, 400 nm, 440 nm, and 480 nm, respectively.