(a) Schematic diagram of a 2D periodic array of nanoantennas. (b) Schematic cross-sectional view, showing how incident light is coupled to a standing wave in the array structure under resonant conditions.
Geometry of the system used in our calculations. Gold nanoblock dimers are attached to a glass surface in an air atmosphere.
(a) xy plot of the normalized electric field intensity on a plane cutting through the middle of the nanoblock thickness. (b) Expanded view of (a) around the gap region. The color plots use a logarithmic scale.
Normalized near-field intensity spectra for a series of array periods. (a) Spectra with a coarse period interval of 100 nm. The strongest peak is found at a period of 500 nm. (b) Spectra with a fine period interval of 10 nm.
Linear plots of the Ex field in the yz plane for incident light of wavelength (a) 795 nm (on-resonance) and (b) 990 nm (off-resonance). Intensities outside the range of the color scale (|Ex| > 2) are shown in white.
Influence of dimer orientation and gap size on near-field spectra. (a) Near-field spectra and (b) wavelength and intensity of spectral peak for different dimer orientations. (c) Near-field spectra and (d) wavelength and intensity of spectral peak for different gap sizes. The array period was fixed at 520 nm.
Normalized near-field intensity spectra for an isolated single-nanogap antenna (bottom panel), finite 3 × 3 (second bottom), and 5 × 5 (second top) arrays and an infinite array structure [top panel, same as in Fig. 4(b) ] for a period of 520 nm.
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