Fig. 1. Structural schematic of asymmetric two nanorods and far field scattering spectra. (a) Top view of structure; (b) xz view of structure; (c) far field scattering spectra of Rl alone, Rs alone and asymmetric nanorod dimers with g = 40 nm and g = 120 nm

Fig. 2. Near field spectra of the asymmetric nanorod dimers with g=40 nm, in which the insets show the morphology of the asymmetric nanorod dimers and label the location of L1, L2, S1 and, S2, respectively, by dots at the end of each rod. (a) Near field spectra of L1 and L2 of Rl, in which the triangle spot-line represents the near field spectrum with the case of Rl alone, and the near field responses of L1 and L2, in this case, are identical; (b) near field spectra of S1 and S2 of Rs, in which the triangle spot-line represents the near field spectrum with the case of Rs alone, and the near field responses of S1 and S2, in this case, are identical

Fig. 3. Near field spectra of L1, L2, S1 and S2 with various of gap size g. (a) L1; (b) L2; (c) S1; (d) S2

Fig. 4. Peak positions of LFM and HFM of L1, L2, S1 and S2 with various of gap size g. (a) LFM; (b) HFM