Figure 1. Plasmonic metasurfaces fabricated on silver-silica-silver three layer structures.

(a) Schematic view of four unit cells for triangular-lattice circular hole arrays fabricated on the silver-silica-silver three layer structure. (b) An example of SEM cross-section image of the metasurface structure with period (P) of 320 nm and hole radius (r) of 100 nm. (c–e) SEM images of three metasurfaces with different lattice geometrical parameters (c: P = 130 nm, r = 35 nm; d: P = 200 nm, r = 50 nm; e: P = 260 nm, r = 65 nm). Insets: Optical reflection microscopy images of the entire 20 × 20 μm² circular hole arrays of triangular lattice. Scale bars: 500 nm.