Figure 3

(a) The transmission spectrum of the structure with L1 = 300 nm and L2 = 180 nm. The two Fano peaks are marked as Fp.1 and Fp.2, which corresponds to the surface charge distribution at the two Fano peaks (723 nm and 870 nm) in the right. (b) The EF of different wavelengths at the maximum enhancement site. The red dotted lines are corresponding to 720 nm, 800 nm and 900 nm. (c) The electric field intensity distribution of the structure with L1 = 300 nm and L2 = 180 nm under the wavelengths of 800 nm, 900 nm and 720 nm.