title: Ultrathin niobium nanofilms on fiber optical tapers--a new route towards low-loss hybrid plasmonic modes.
abstract: Due to the ongoing improvement in nanostructuring technology, ultrathin metallic nanofilms have recently gained substantial attention in plasmonics, e.g. as building blocks of metasurfaces. Typically, noble metals such as silver or gold are the materials of choice, due to their excellent optical properties, however they also possess some intrinsic disadvantages. Here, we introduce niobium nanofilms (~10 nm thickness) as an alternate plasmonic platform. We demonstrate functionality by depositing a niobium nanofilm on a plasmonic fiber taper, and observe a dielectric-loaded niobium surface-plasmon excitation for the first time, with a modal attenuation of only 3-4 dB/mm in aqueous environment and a refractive index sensitivity up to 15 μm/RIU if the analyte index exceeds 1.42. We show that the niobium nanofilm possesses bulk optical properties, is continuous, homogenous, and inert against any environmental influence, thus possessing several superior properties compared to noble metal nanofilms. These results demonstrate that ultrathin niobium nanofilms can serve as a new platform for biomedical diagnostics, superconducting photonics, ultrathin metasurfaces or new types of optoelectronic devices.
authors.affiliation: Leibniz Institute of Photonic Technology e.V., Albert-Einstein-Str. 9, 07745 Jena, Germany.
authors.forename: Torsten
authors.initials: T
authors.lastname: Wieduwilt
authors.affiliation: Leibniz Institute of Photonic Technology e.V., Albert-Einstein-Str. 9, 07745 Jena, Germany.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Tuniz
authors.affiliation: Leibniz Institute of Photonic Technology e.V., Albert-Einstein-Str. 9, 07745 Jena, Germany.
authors.forename: Sven
authors.initials: S
authors.lastname: Linzen
authors.affiliation: Leibniz Institute of Photonic Technology e.V., Albert-Einstein-Str. 9, 07745 Jena, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Goerke
authors.affiliation: Leibniz Institute of Photonic Technology e.V., Albert-Einstein-Str. 9, 07745 Jena, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Dellith
authors.affiliation: Leibniz Institute of Photonic Technology e.V., Albert-Einstein-Str. 9, 07745 Jena, Germany.
authors.forename: Uwe
authors.initials: U
authors.lastname: Hübner
authors.affiliation: Leibniz Institute of Photonic Technology e.V., Albert-Einstein-Str. 9, 07745 Jena, Germany.|Otto Schott Institute of Material Research, Fraunhoferstr.6, Friedrich-Schiller-University, 07743 Jena, Germany.|Abbe Center of Photonics, Friedrich-Schiller-University, Max-Wien-Platz 1, 07743 Jena, Germany.
authors.forename: Markus A
authors.initials: MA
authors.lastname: Schmidt