title: Experimental verification of n = 0 structures for visible light.
abstract: We fabricate and characterize a metal-dielectric nanostructure with an effective refractive index n = 0 in the visible spectral range. Light is excited in the material at deep subwavelength resolution by a 30-keV electron beam. From the measured spatially and angle-resolved emission patterns, a vanishing phase advance, corresponding to an effective [Symbol: see text] = 0 and n = 0, is directly observed at the cutoff frequency. The wavelength at which this condition is observed can be tuned over the entire visible or near-infrared spectral range by varying the waveguide width. This n = 0 plasmonic nanostructure may serve as a new building block in nanoscale optical integrated circuits and to control spontaneous emission as experimentally demonstrated by the strongly enhanced radiative optical density of states over the entire n = 0 structure.
authors: Center for Nanophotonics, FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, Netherlands.
authors: Ernst Jan R
authors: EJ
authors: Vesseur
authors: Toon
authors: T
authors: Coenen
authors: Humeyra
authors: H
authors: Caglayan
authors: Nader
authors: N
authors: Engheta
authors: Albert
authors: A
authors: Polman