Figure 1. Prominent Fano resonances in 3D MMs.

(a) Schematic of the unit cell of a 3D MM in which the vertical SRR or vertical plate (SRR filled with the grey area) is conductively connected to one edge of a metallic hole. The free-standing structure is completely composed of Au without any substrate. (b,c) Side-view SEM images of the fabricated 3D MMs with (a) vertical SRRs and (b) vertical plates, respectively. Scale bars: 500 nm. (d) As-measured and (e) calculated transmission spectra of an EOT structure without any vertical structure and two 3D MMs with different vertical structures under y-polarized light excitation. The Fano resonances of the two 3D MMs are well preserved under the dramatic structural changes. Structural parameters: p = 750 nm, a = 560 nm, d = 50 nm; l = 430 nm, h = 560 nm, w = 150 nm; width and height of the vertical plates: l_p = 430 nm, h_p = 560 nm. (f) Measured and calculated transmission spectra of a 3D MM under y-polarized light excitation in the mid-infrared wavelength region, agreeing very well with each other. Structural parameters: p = 3 μm, a = 2μm, d = 80 nm, l = 1 μm, h = 1.45 μm, w = 0.25 μm.