Schematic drawing of trapezoid-shaped triple-layer (Ag-SiO₂-Ag) nanorod array on glass substrate with geometric parameters of P_x = 200 nm, P_y = 1000 nm, W_s = 40 nm, W_l = 150 nm and L = 800 nm. The triple-layer nanorod thickness is 30 nm (Ag), 40 nm (SiO₂) and 30 nm (Ag), respectively. Broadband white source is normally (along z-axis) incident onto the sample surface with the electric-field polarized along x-axis.