Probing surface plasmons by bare V-shaped tips: modeling by geometrical optics and rigorous diffraction theory
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We consider probing inhomogeneous waves in the near fields of metallic nanostructures with the aid of a dielectric V-shaped wedge connected to a waveguide. A geometrical model based on the local plane interface approach is proposed to describe the interaction of the wedge with the inhomogeneous field. The fundamental ideas behind the geometrical model are validated by comparison with the results given by rigorous diffraction analysis, and applied to probing plasmonic interference patterns generated by metallic gratings with very narrow slits. The model explains intuitively why a bare wedge with a large apex angle is capable of subwavelength resolution in the spirit of scanning near-field microscopy.
KeywordsNanophotonics Diffractive optics Geometrical optics Plasmonics
The work was supported by the Academy of Finland (Project 285880). J. Tervo is presently with Microsoft HoloLens, Keilalahdentie 2–4, 02150 Espoo, Finland.
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