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Scanning election microscopy images of the sample containing eight concentric arcs in plane view (a) and in cross section (b). Panel (a) defines the distances and angles appearing in the model calculations [Eq. (1)]. “x” is the point of observation and “c” marks the center of the arcs.
(Color online) Panels (a)–(c) show NSOM images of the SPP distribution in samples containing eight, four, and two arcs, respectively, for incident light with wavelength of polarized parallel to the symmetry axis; the circles in panel (c) indicate the areas from which light for Raman spectroscopy was collected; panel (d) shows the image for the eight-arc sample for perpendicular polarization. Intensity profiles along the vertical and horizontal directions through the focal spot of the eight-arc sample are shown in panel (e). The width of the focal spot at half maximum is . Included are fits according to the model [Eq. (1)]. Panel (f) shows the variation of the intensity at the focal spot with the number of arcs . The lines represent model calculations for different values of the transmission coefficient .
Stokes Raman spectra of R6G taken with incident light on a silver structure with one arc (a) and four arcs (b), respectively. The stars mark the dominant Raman lines of R6G. Spectra for parallel incident polarization (vertical axis in Fig. 2) and perpendicular polarization are shown. Also included are spectra from an area displaced from the focal spot [bottom curve in Fig. 3(b)].
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