title: Imaging of Anomalous Internal Reflections of Hyperbolic Phonon-Polaritons in Hexagonal Boron Nitride.
abstract: We use scanning near-field optical microscopy to study the response of hexagonal boron nitride nanocones at infrared frequencies, where this material behaves as a hyperbolic medium. The obtained images are dominated by a series of "hot" rings that occur on the sloped sidewalls of the nanocones. The ring positions depend on the incident laser frequency and the nanocone shape. Both dependences are consistent with directional propagation of hyperbolic phonon-polariton rays that are launched at the edges and zigzag through the interior of the nanocones, sustaining multiple internal reflections off the sidewalls. Additionally, we observe a strong overall enhancement of the near-field signal at discrete resonance frequencies. These resonances attest to low dielectric losses that permit coherent standing waves of the subdiffractional polaritons to form. We comment on potential applications of such shape-dependent resonances and the field concentration at the hot rings.
authors.affiliation: U.S. Naval Research Laboratory , 4555 Overlook Avenue, S.W., Washington, DC 20375, United States.
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Giles
authors.affiliation: Department of Physics, University of California San Diego , 9500 Gilman Drive, La Jolla, California 92093, United States.
authors.forename: Siyuan
authors.initials: S
authors.lastname: Dai
authors.affiliation: U.S. Naval Research Laboratory , 4555 Overlook Avenue, S.W., Washington, DC 20375, United States.
authors.forename: Orest J
authors.initials: OJ
authors.lastname: Glembocki
authors.affiliation: School of Physics and Astronomy, University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom.
authors.forename: Andrey V
authors.initials: AV
authors.lastname: Kretinin
authors.affiliation: Department of Physics, University of California San Diego , 9500 Gilman Drive, La Jolla, California 92093, United States.
authors.forename: Zhiyuan
authors.initials: Z
authors.lastname: Sun
authors.affiliation: U.S. Naval Research Laboratory , 4555 Overlook Avenue, S.W., Washington, DC 20375, United States.
authors.forename: Chase T
authors.initials: CT
authors.lastname: Ellis
authors.affiliation: U.S. Naval Research Laboratory , 4555 Overlook Avenue, S.W., Washington, DC 20375, United States.
authors.forename: Joseph G
authors.initials: JG
authors.lastname: Tischler
authors.affiliation: National Institute for Materials Science , 1-1 Namiki Tsukuba, Ibaraki 305-0047, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Taniguchi
authors.affiliation: National Institute for Materials Science , 1-1 Namiki Tsukuba, Ibaraki 305-0047, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: Department of Physics, University of California San Diego , 9500 Gilman Drive, La Jolla, California 92093, United States.
authors.forename: Michael M
authors.initials: MM
authors.lastname: Fogler
authors.affiliation: School of Physics and Astronomy, University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom.
authors.forename: Kostya S
authors.initials: KS
authors.lastname: Novoselov
authors.affiliation: Department of Physics, University of California San Diego , 9500 Gilman Drive, La Jolla, California 92093, United States.|Department of Physics, Columbia University , 538 West 120th Street, New York, New York 10027, United States.
authors.forename: Dimitri N
authors.initials: DN
authors.lastname: Basov
authors.affiliation: U.S. Naval Research Laboratory , 4555 Overlook Avenue, S.W., Washington, DC 20375, United States.
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Caldwell
keywords: 2D materials; Near-field imaging; hexagonal boron nitride; hyperbolic materials; phonon-polaritons; subdiffractional focusing; tunable nanoresonators; van der Waals