Figure 3. Simulated and measured optical properties and effective medium parameters of the fabricated modified fishnet nanostructure.

(a) Simulated and measured transmission (top, blue) and reflection (middle, red) magnitudes for normally incident radiation showing broadband transmission over the highlighted region from 3.0 μm to 3.5 μm. Simulated group delay τ_g (bottom) shows minimal variation over the transmission window. (b) Real (top) and imaginary (bottom) parts of the effective index of refraction n_eff (green), permittivity ε_eff (red), permeability μ_eff (blue), and impedance Z_eff (orange) retrieved from the full-wave simulation of the metamaterial structure. The real parts of ε_eff and μ_eff follow a similar slope from 3.0 μm to 3.5 μm, indicating a matched impedance, whereas the imaginary parts are small, indicating low intrinsic losses.