title: Near-field visualization of strongly confined surface plasmon polaritons in metal-insulator-metal waveguides.
abstract: A nanoscale gap between two metal surfaces can confine propagating surface plasmon polaritons (SPPs) to very small dimensions, but this geometry makes it inherently difficult to image SPP propagation at high resolution. We demonstrate the near-field probing of these SPPs, propagating within a 50 nm thick Si 3N 4 waveguide with Ag cladding layers for frequencies ranging from the blue to the near-infrared. Using near-field SPP interferometry, we determine the wave vector, showing that the wavelength is shortened to values as small as 156 nm for a free-space wavelength of 532 nm.
authors.affiliation: Center for Nanophotonics, FOM Institute for Atomic and Molecular Physics, Kruislaan 407, 1098 SJ Amsterdam, The Netherlands. verhagen@amolf.nl
authors.forename: Ewold
authors.initials: E
authors.lastname: Verhagen
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Dionne
authors.forename: L Kobus
authors.initials: LK
authors.lastname: Kuipers
authors.forename: Harry A
authors.initials: HA
authors.lastname: Atwater
authors.forename: Albert
authors.initials: A
authors.lastname: Polman