Figure 21.

(a) Reflection (schematic) from a nanostructured gold film. (b) The phase Δ, of p-polarized light for the structure shown in (a) as a function of wave-vector calculated with the effective medium theory for θ = 60°, array period = 320 nm, gold and PMMA height 90 nm, PMMA stripe width 165 nm. The blue line marks the smooth phase behavior away from the zero reflection condition, the yellow line marks the phase jump. (c) The dispersion curves for plane gold and nanostructured gold along with their ellipsometric reflection spectra. For the nanostructured gold, it is seen that the dispersion curve can pass through the zero reflection condition (brown curve) and the reflection attains exactly the value zero, which is topologically protected. Reproduced and adapted with permission from ref (39). Copyright 2013 Nature Publishing Group.