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Figure 6: Finite-difference time-domain (FDTD) simulation of the electromagnetic field distributions of the different-sized AuNPs line. The gap between AuNPs is 10.6 nm (a), 12.7 nm (b), 2.7 nm (c), 2.8 nm (d), 5.9 nm (e), and 5.5 nm (f), respectively. The incident light is along x axis direction.