(a) Total absorption calculated as 1-reflectivity shows resonant modes in Si₃N₄–Si and overall lower absorption in the nanostructured sample. (b) Distribution of electric field intensity and absorption density in Si₃N₄–Si strongly depends on Si behavior at cavity resonant wavelengths. (c) Partial absorption is calculated by integrating absorption density over first 5 μm or 10 μm of Si in Si and Si₃N₄–Si, and adding the Au part for Au–Si₃N₄–Si and Nano-Au–Si₃N₄–Si. (d) Total absorption of Au ENHA on Si₃N₄ shows resonant absorption peak at 894 nm. (e) Electric field intensity and absorption density in the first 2 μm of depth of the three samples.