title: Influence of the dielectric substrate on the terahertz electric near-field of a hole in a metal.
abstract: We have studied theoretically and experimentally the influence of a dielectric substrate on the frequency-dependent terahertz electric near-field of a small hole in a metal layer. We find that the near-field transmission spectrum and the two-dimensional field distribution of an empty hole in a thin metal layer on a substrate are almost identical to that of a hole which is also filled with the same dielectric material as the substrate. For thicker metal layers, however, the near-field spectra of filled and unfilled holes become very different. In addition, for thick metal layers, the two-dimensional field distributions are more strongly affected by the substrate, especially if we allow for an air gap between the metal and the substrate. Our results validate the -somewhat unusual- two-dimensional field distribution measured beneath a hole in a thick metal foil and highlight the effect that a substrate can have on the measurement of the near-field of an object.
authors.affiliation: Delft University of Technology, Faculty of Applied Sciences, Department of Imaging Science and Technology, Optics Research Group Lorentzweg 1, 2628 CJ Delft, The Netherlands.
authors.forename: L
authors.initials: L
authors.lastname: Guestin
authors.forename: A J L
authors.initials: AJ
authors.lastname: Adam
authors.forename: J R
authors.initials: JR
authors.lastname: Knab
authors.forename: M
authors.initials: M
authors.lastname: Nagel
authors.forename: P C M
authors.initials: PC
authors.lastname: Planken
mesh_terms: D003198:Computer Simulation; D008670:Metals; D008962:Models, Theoretical; D012031:Refractometry / Q000379:methods*; D012542:Scattering, Radiation; D055053:Terahertz Radiation; D055068:Terahertz Spectroscopy / Q000379:methods*
chemical_list: D008670:Metals