title: Boosting Local Field Enhancement by on-Chip Nanofocusing and Impedance-Matched Plasmonic Antennas.
abstract: Strongly confined surface plasmon-polariton modes can be used for efficiently delivering the electromagnetic energy to nanosized volumes by reducing the cross sections of propagating modes far beyond the diffraction limit, that is, by nanofocusing. This process results in significant local-field enhancement that can advantageously be exploited in modern optical nanotechnologies, including signal processing, biochemical sensing, imaging, and spectroscopy. Here, we propose, analyze, and experimentally demonstrate on-chip nanofocusing followed by impedance-matched nanowire antenna excitation in the end-fire geometry at telecom wavelengths. Numerical and experimental evidence of the efficient excitation of dipole and quadrupole (dark) antenna modes are provided, revealing underlying physical mechanisms and analogies with the operation of plane-wave Fabry-Pérot interferometers. The unique combination of efficient nanofocusing and nanoantenna resonant excitation realized in our experiments offers a major boost to the field intensity enhancement up to ∼12000, with the enhanced field being evenly distributed over the gap volume of 30 × 30 × 10 nm(3), and promises thereby a variety of useful on-chip functionalities within sensing, nonlinear spectroscopy and signal processing.
authors.affiliation: Centre for Nano Optics, University of Southern Denmark , Campusvej 55, DK-5230 Odense M, Denmark.
authors.forename: Vladimir A
authors.initials: VA
authors.lastname: Zenin
authors.affiliation: DTU Fotonik, Technical University of Denmark , Oersteds pl. 343, DK-2800 Kongens Lyngby, Denmark.
authors.forename: Andrei
authors.initials: A
authors.lastname: Andryieuski
authors.affiliation: DTU Fotonik, Technical University of Denmark , Oersteds pl. 343, DK-2800 Kongens Lyngby, Denmark.
authors.forename: Radu
authors.initials: R
authors.lastname: Malureanu
authors.affiliation: Centre for Nano Optics, University of Southern Denmark , Campusvej 55, DK-5230 Odense M, Denmark.
authors.forename: Ilya P
authors.initials: IP
authors.lastname: Radko
authors.affiliation: Centre for Nano Optics, University of Southern Denmark , Campusvej 55, DK-5230 Odense M, Denmark.
authors.forename: Valentyn S
authors.initials: VS
authors.lastname: Volkov
authors.affiliation: Nanophotonics Pty. Ltd. , GPO Box 786, Albany Creek, Queensland 4035, Australia.
authors.forename: Dmitri K
authors.initials: DK
authors.lastname: Gramotnev
authors.affiliation: DTU Fotonik, Technical University of Denmark , Oersteds pl. 343, DK-2800 Kongens Lyngby, Denmark.
authors.forename: Andrei V
authors.initials: AV
authors.lastname: Lavrinenko
authors.affiliation: Centre for Nano Optics, University of Southern Denmark , Campusvej 55, DK-5230 Odense M, Denmark.
authors.forename: Sergey I
authors.initials: SI
authors.lastname: Bozhevolnyi
keywords: Surface plasmons polaritons; field enhancement; nanofocusing; optical antennas; phase-resolved near-field microscopy; tapered waveguide