Figure 2: Reflectivity of 1D groove arrays in gold.
From: Plasmonic black gold by adiabatic nanofocusing and absorption of light in ultra-sharp convex grooves
Scanning electron microscopy images of (a) 350-nm-period array of ultra-sharp 450-nm-deep grooves milled in gold (scale bar, 1 μm) displaying slight period variations and surface roughness (see inset), and (b) its cross-section, revealing a convex shape of the grooves (scale bar, 300 nm) and demonstrating negligibly small wall inclination angles, α 
0° (Fig. 1b). (c,d) Reflectivity spectra of (c) s-polarized (along the x axis) and (d) p-polarized (along the y axis) light for 450-nm-deep convex grooves with different inclination angles α arranged in 1D arrays with different periods Λ, shown with green (α=14°, Λ=350 nm), red (α=9°, Λ=350 nm), blue (α=0°, Λ=350 nm) and black (α=0°, Λ=250 nm) dashed (s-polarization) and solid (p-polarization) lines. Reflectivity spectrum for a flat gold surface is shown with a solid yellow line in c. Insets display optical microscope images (scale bar, 20 μm) of the 250-nm-period array of ultra-sharp (α 0°) 450-nm-deep grooves obtained for two orthogonal polarizations of incident light (polarization directions are indicated with arrows in the insets).
