Channel-plasmon nanofocusing

Abstract:

Recent, rapid developments in plasmonic circuitry1 suggest numerous possibilities for practical applications of optical phenomena associated with metal nanostructures. Nanoscale field confinement through surface-plasmon (SP) manipulation has great potential to revolutionize many applications in nanophotonics, ranging from quantum optics2 to imaging, 3 near-field optics, 4, 5 and nanosensing. 6 Various SP-focusing geometries have been suggested to achieve high SP concentrations on scales smaller than the diffraction limit of light (in the surrounding dielectric material). They all support progressively stronger confined SP modes in the limit of infinitely small waveguide cross sections. 7–14 The idea of radiation (nano-) focusing (and simultaneously greatly enhancing electromagnetic fields) by gradually decreasing a waveguide cross section is very appealing because of its apparent simplicity. Realization, however, requires the waveguide mode to scale in size along with its cross section, a nontrivial characteristic that is not readily accessible and, for example, cannot be achieved with dielectric waveguides because of the diffraction limit. The physics underlying SP guiding is fundamentally different to and intimately connected with the hybrid nature of SP modes, in which electromagnetic fields in dielectrics are coupled to free-electron oscillations in metals. 15 In the limit of infinitely small waveguides, several SP-guiding configurations exhibit the requisite scale invariance (ie, the mode size scales linearly with that of the waveguide). The appropriate SP modes are supported, for example, by thin metal films (short-range SPs) and narrow gaps …

Año de publicación:

1997

Keywords:

Fuente:

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