title: Hybrid-Mode-Assisted Long-Distance Excitation of Short-Range Surface Plasmons in a Nanotip-Enhanced Step-Index Fiber.
abstract: We propose and experimentally demonstrate a monolithic nanowire-enhanced fiber-based nanoprobe for the broadband delivery of light (550-730 nm) to a deep subwavelength scale using short-range surface plasmons. The geometry is formed by a step index fiber with an integrated gold nanowire in its core and a protruding gold nanotip with sub-10 nm apex radius. We present a novel coupling scheme to excite short-range surface plasmons, whereby the radially polarized hybrid mode propagating inside the nanowire section excites the plasmonic mode close to the fiber endface, which is in turn superfocused down to nanoscale dimensions at the tip apex. We show that in this all-integrated fiber-plasmonic coupling scheme the wire length can be orders of magnitude longer than the attenuation length of short-range plasmon polaritons, yielding a broadband plasmon excitation and reducing demands in fabrication. We observe that the scattered light in the far-field from the nanotip is axially polarized and preferentially excited by a radially polarized input, unambiguously revealing that it originates from a short-range plasmon propagating on the nanotip, in agreement with simulations. This novel excitation scheme will have important applications in near-field microscopy and nanophotonics and potentially offers significantly improved resolution compared to current delivery near-field probes.
authors.affiliation: Leibniz Institute of Photonic Technology (IPHT Jena) , Albert-Einstein-Strasse 9, 07745 Jena, Germany.
authors.forename: Alessandro
authors.identifier: 0000-0002-3950-6282
authors.initials: A
authors.lastname: Tuniz
authors.affiliation: Leibniz Institute of Photonic Technology (IPHT Jena) , Albert-Einstein-Strasse 9, 07745 Jena, Germany.|Abbe School of Photonics and Faculty of Physics , Max-Wien-Platz 1, 07743 Jena, Germany.
authors.forename: Mario
authors.initials: M
authors.lastname: Chemnitz
authors.affiliation: Leibniz Institute of Photonic Technology (IPHT Jena) , Albert-Einstein-Strasse 9, 07745 Jena, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Dellith
authors.affiliation: Leibniz Institute of Photonic Technology (IPHT Jena) , Albert-Einstein-Strasse 9, 07745 Jena, Germany.|Heraeus Quarzglas GmbH & Co. KG, Quarzstrasse 8, 63450 Hanau, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Weidlich
authors.affiliation: Leibniz Institute of Photonic Technology (IPHT Jena) , Albert-Einstein-Strasse 9, 07745 Jena, Germany.|Abbe School of Photonics and Faculty of Physics , Max-Wien-Platz 1, 07743 Jena, Germany.|Otto Schott Institute of Materials Research , Fraunhoferstrasse 6, 07743 Jena, Germany.
authors.forename: Markus A
authors.initials: MA
authors.lastname: Schmidt
keywords: Plasmonic tip; SNOM; hybrid fibers; radially polarized SPP