title: Imaging of electric and magnetic fields near plasmonic nanowires.
abstract: Near-field imaging is a powerful tool to investigate the complex structure of light at the nanoscale. Recent advances in near-field imaging have indicated the possibility for the complete reconstruction of both electric and magnetic components of the evanescent field. Here we study the electro-magnetic field structure of surface plasmon polariton waves propagating along subwavelength gold nanowires by performing phase- and polarization-resolved near-field microscopy in collection mode. By applying the optical reciprocity theorem, we describe the signal collected by the probe as an overlap integral of the nanowire's evanescent field and the probe's response function. As a result, we find that the probe's sensitivity to the magnetic field is approximately equal to its sensitivity to the electric field. Through rigorous modeling of the nanowire mode as well as the aperture probe response function, we obtain a good agreement between experimentally measured signals and a numerical model. Our findings provide a better understanding of aperture-based near-field imaging of the nanoscopic plasmonic and photonic structures and are helpful for the interpretation of future near-field experiments.
authors.affiliation: FOM Institute AMOLF, Science park 104, 1098 XG Amsterdam, The Netherlands.|Blackett Laboratory, Imperial College London, London SW7 2AZ, United Kingdom.
authors.forename: I V
authors.initials: IV
authors.lastname: Kabakova
authors.affiliation: FOM Institute AMOLF, Science park 104, 1098 XG Amsterdam, The Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: de Hoogh
authors.affiliation: FOM Institute AMOLF, Science park 104, 1098 XG Amsterdam, The Netherlands.
authors.forename: R E C
authors.initials: RE
authors.lastname: van der Wel
authors.affiliation: FOM Institute AMOLF, Science park 104, 1098 XG Amsterdam, The Netherlands.|Institute of Science and Technology Austria, Am Campus 1, A-3400 Klosterneuburg, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Wulf
authors.affiliation: FOM Institute AMOLF, Science park 104, 1098 XG Amsterdam, The Netherlands.|Optical Materials Laboratory, ETH Zurich, 8092 Zurich, Switzerland.
authors.forename: B
authors.initials: B
authors.lastname: le Feber
authors.affiliation: FOM Institute AMOLF, Science park 104, 1098 XG Amsterdam, The Netherlands.
authors.forename: L
authors.initials: L
authors.lastname: Kuipers