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Real-space mapping of nanoplasmonic hotspots via optical antenna-gap loading
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View: Figures


Image of FIG. 1.
FIG. 1.

s-SNOM images of topography (1a, f), 4th harmonic amplitude (1b,c, g, h) and phase (1d, e, i, j) images gold IR antennas on SiO2 substrate. In1b, d an S/P polarization is used, compared to an S/S scheme shown inallother figures. (f)–(j) show a zoomed-in image of the gap region at ω = 978 cm−1 (1g, i) and ω = 952 cm−1 (1h, j), showing maximum enhancement at the latter.

Image of FIG. 2.
FIG. 2.

Experimental zoom-in 4th harmonic s-SNOM images for gaps 30 nm (a), 48 nm (b), 53 nm (c), and 61 nm (c) taken using ω = 952 cm−1 excitation laser. (e) Plot of the normalized amplitude at the hotspot as function of gap width, with the dotted line shown as a guide to the eye.

Image of FIG. 3.
FIG. 3.

s-SNOM images of topography (a), amplitude (b), (c), and phase (d), (e) of the nanoantenna gap region imaged using a Si tip (b), (d) and a PtIr-coated tip (c), (e). (f)–(i) show FDTD simulated near-field distribution of the antennas taken at ω = 952 cm−1; both used a 50 nm gap and 40 nm block of Si (3f, h) and Pt (3g, i) inside the gap. (h) and (i) show zoom-in image of the gap region for Si and Pt loading, respectively. (j) shows a schematic (not to-scale) of the loaded antenna atop the glass substrate used for FDTD simulations and impedance calculations: the rod dimensions used were 1811 nm long, 95 nm wide, 32 nm thick, with 50 nm gap. (k) shows the calculated reactance versus complex dielectric constant, for a 50 nm gap that is filled with material; note that (0, 0) is a discontinuity.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Real-space mapping of nanoplasmonic hotspots via optical antenna-gap loading