title: Real-Space Mapping of the Chiral Near-Field Distributions in Spiral Antennas and Planar Metasurfaces.
abstract: Chiral antennas and metasurfaces can be designed to react differently to left- and right-handed circularly polarized light, which enables novel optical properties such as giant optical activity and negative refraction. Here, we demonstrate that the underlying chiral near-field distributions can be directly mapped with scattering-type scanning near-field optical microscopy employing circularly polarized illumination. We apply our technique to visualize, for the first time, the circular-polarization selective nanofocusing of infrared light in Archimedean spiral antennas, and explain this chiral optical effect by directional launching of traveling waves in analogy to antenna theory. Moreover, we near-field image single-layer rosette and asymmetric dipole-monopole metasurfaces and find negligible and strong chiral optical near-field contrast, respectively. Our technique paves the way for near-field characterization of optical chirality in metal nanostructures, which will be essential for the future development of chiral antennas and metasurfaces and their applications.
authors.affiliation: CIC nanoGUNE , 20018 Donostia - San Sebastián, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Schnell
authors.affiliation: CIC nanoGUNE , 20018 Donostia - San Sebastián, Spain.
authors.forename: P
authors.initials: P
authors.lastname: Sarriugarte
authors.affiliation: Centro de Fisica de Materiales CSIC-UPV/EHU and Donostia International Physics Center DIPC , 20018 Donostia - San Sebastián, Spain.
authors.forename: T
authors.initials: T
authors.lastname: Neuman
authors.affiliation: Department of Physics, Queens College and Graduate Center of The City University of New York , New York, NewYork, 11367, United States.
authors.forename: A B
authors.initials: AB
authors.lastname: Khanikaev
authors.affiliation: Department of Physics, The University of Texas at Austin , Austin, Texas 78712, United States.
authors.forename: G
authors.initials: G
authors.lastname: Shvets
authors.affiliation: Centro de Fisica de Materiales CSIC-UPV/EHU and Donostia International Physics Center DIPC , 20018 Donostia - San Sebastián, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Aizpurua
authors.affiliation: CIC nanoGUNE and EHU/UPV , 20018 Donostia - San Sebastián, Spain.|IKERBASQUE, Basque Foundation for Science , 48011 Bilbao, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Hillenbrand
keywords: Optical antennas; SNOM; metasurfaces; near-field microscopy; optical chirality; plasmonics