Figure 4.

Effect of diameter on the transmission resonances excited in a coaxial aperture array. (a–d) SEM images of coaxial aperture arrays with 100, 150, 200, and 250 nm diameters, respectively. (e) The transmitted spectra from the coaxial 10 nm gap with 100, 150, 200, 250 nm diameters. (f) The dispersion curve of the plasmonic coaxial aperture. FP0 (m = 0), FP1 (m = 1), and FP2 (m = 2) resonances (experimental data) are fitted with the analytical dispersion curve. (g) Photograph of a 4-in. wafer fully patterned with dense arrays of nanocavities with various shapes. Zoomed-in SEM images of wafer-scale arrays of (h) coaxial nanocavities, (i) triangular nanocavities, and (j) concentric annular nanocavities. These arrays were patterned via photolithography. Scale bars: (a–d) 150 nm, (h–j) 1 μm.