SUPPORTING INFORMATION

Fanointerferencebetweenhigher localized and propagating surface plasmon modes in nanovoid arrays

Shu Chen1, Lingyan Meng1,Jiawen Hu2,*,Zhilin Yang1,*

1Department of Physics, Xiamen University, Xiamen 361005, China.

2College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China.

*;

EM field distributions on a single,isolated nanovoid

As explained in the text, dark mode cannot be directly excited by far-field incident light, but can be indirectly excited by the near-fieldsassociated with the bright mode[1, 2]. In this study, the (1, 0) surface plasmon polariton (SPP) mode is the bright mode and serves as the excitation source of the dark mode. Because the (1, 0) SPP mode is intrinsic to theperiodic nature of the Au SSV nanovoid arrays (see equation 1 in the text),to decouple its interaction with the dark mode we simulated the optical properties for a single, isolated nanovoid. To scan the dark modes, we selected four excitation lights of 550, 609, 663,and 750 nm, among which the 609 and 663 nmlights are the positions of the two Fano dips and thus are nearby the dark quadrupolar and hexadecapolar modes, respectively. Fig. S1indicates that all the EM distributions show dipolar-like patterns, with no quadrupolar and hexadecapolar field patterns observed.These simulations reveal that the quadrupolar and hexadecapolarmodesindeed cannot be directly excited by far-field incident light even the light is close totheir resonance frequencies, thereby confirming their “dark” nature.

Fig. S1. EM field distributions in the xy plane of a single,isolated nanovoid with D = 600 nm, H = 510 nm, and P=600 nm excited using lights of550 (a), 609 (b), 663 (c), and 750nm (d).The local electric field |E|4is shown under logarithmic coordinatesand is normalized by the fourth power of the strength of the incident light.

EM field distributions on (100) patternednanovoid arrays

Fig. S2shows theEM field distributions in the xy-plane of the (100) patterned Au SSV nanovoid arrays for optical excitation of the dipole modeat 910 nm, the (1,0) SPP modeat 650 nm, and the two Fano dips at 663 and 609 nm. Only anisolated, dipolar field patternis observed for the dipole mode generates (Fig. 2Sa),indicating little coupling interactions from other modes.In contrast, mixed field pattern of the quadrupolar and hexadecapolar modes(at the edges of the voids)and surface-bound fields (on the flat Au surfaces among nearby Au nanovoids) are observed for the (1,0) SPP mode(Fig. 2S c). Thequadrupolar and hexadecapolarpatterns are more isolated and typical for the two Fano dips, and are also companied with the surface-bound fields (Fig. 2Sb and d). They, however, are not observed on a single, isolated Au nanovoid which is intentially used to decouples the (1.0) SPP mode (Fig. 1S). Thesesimulationsfurther reveal it is the surface-bound fields associated with the the (1,0) SPP mode that excite the dark quadrupole and hexacapolar modes.

Fig. S2. EM field distributions in thexy-plane of the (100) patternedAu SSVnanovoid arrays with D = 600 nm, H = 510 nm, and P=600 nm, which were simulated at  = 910，650, 663 and 609 nm and correspondto optical excitation of the dipole mode at 910 nm (a), the (1,0) mode at 650 nm (c), and the two Fano dips at 663 and 609 nm(band d).

References

1.J. H. Naomi, S. Lal, W. S. Chang, S. Link, and P. Nordlander,“Plasmons in strongly coupled metallic nanostructures,” Chem. Rev. 111, 3913–3961(2011).

2.J. A. Fan, K. Bao, C. H. Wu, J. M. Bao, R. Bardhan, N. J. Halas, V. N. Manoharan, G. Shvets, P. Nordlancer, and F. Capasso, “Fano-like interference in self-assembled plasmonic quadrumer clusters,” Nano Lett. 10, 4680-4685(2010).