Fig. 1. (a) and (b): Real part and imaginary part of the dielectric function of bulk silver from various sources in the literature, J&C [12], L&H [13], and Weber [14]; (c) The same as (b) but only the visible range; (d) Imaginary part of the bulk Ag dielectric function: experiment Ref. [12] (red crosses), Drude-Lorentz approximation (dashed orange line), Drude term (blue solid line).

Fig. 2. Paired strips geometry with different roughness. (a) Ideal structure, δ=0, (b) δ=1.5nm, and (c) δ=2.0nm.

Fig. 3. Example of field emission scanning electron microscope and atomic force microscope images (sample #2).

Fig. 4. TM polarization spectra (a)–(c): (a) simulated (dashed lines) spectra of transmission (blue), reflection (red), and absorption (orange) for one of the samples (sample #4) calculated with different the RMS surface roughness vs. the experimental data (solid lines); (b) simulated effective optical density D obtained for the RMS surface roughness (orange, δ=1.7 nm, purple, δ=2.3 nm, and blue, δ=2.9 nm) vs. the experimental data (red). (c) simulated effective optical density D obtained for the RMS surface roughness (orange, δ=1.7, blue, δ=2.3, and purple, δ=2.9). TE polarization spectra (d): experimental (solid lines) and simulated (dashed lines) spectra of transmission (blue), reflection (red), and effective optical density (orange).

Fig. 5. The experimental spectra of the imaginary part of the Ag dielectric function in the coupled strips for five samples in comparison with the bulk dielectric function from two sources J&C, Ref. [12] and L&H, Ref. [13] for TE (a) and TM (b) polarizations.

Fig. 6. (a) Size dependent term of the relaxation rate (eV) versus the inverse effective width of the strips for TM (blue squares) and TE (red circles) polarizations. (b) the real part of effective permeability vs. the RMS of surface roughness.