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  • Review Article
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Nanofocusing of electromagnetic radiation

Abstract

Nanofocusing of electromagnetic radiation, that is, reducing the cross sections of propagating optical modes far beyond the diffraction limit in dielectric media, can be achieved in tapered metal–dielectric waveguides that support surface plasmon–polariton modes. Although the main principles of nanofocusing were formulated over a decade ago, a deep theoretical understanding and conclusive experimental verification were achieved only a few years ago. These advances have spawned a variety of new important technological possibilities for the efficient delivery, control and manipulation of optical radiation on the nanoscale. Here, we present the underlying physical principles of radiation nanofocusing in metallic nanostructures, overview recent progress and major developments, and consider future directions and potential applications of this subfield of nano-optics.

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Figure 1: Insulator–metal–insulator and metal–insulator–insulator nanofocusing configurations.
Figure 2: Metal–insulator–metal and hybrid nanofocusing configurations.
Figure 3: Typical field distributions in nanofocusing structures.
Figure 4: Plasmon nanofocusing configurations with tapered nanowires.
Figure 5: Plasmonic nanofocusing configurations with tapered gaps.

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Acknowledgements

S.I.B. acknowledges financial support from the Danish Council for Independent Research (FTP contract No. 09-072949 ANAP).

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Gramotnev, D., Bozhevolnyi, S. Nanofocusing of electromagnetic radiation. Nature Photon 8, 13–22 (2014). https://doi.org/10.1038/nphoton.2013.232

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