title: Optical properties of single plasmonic holes probed with local electron beam excitation.
abstract: Similar to nanoparticles, nanoscale holes form a basic building block in a wide array of nanophotonic devices. Here we study the spectral and angular cathodoluminescence response of individual nanoholes with diameters ranging from 50 to 180 nm. Taking advantage of the deep-subwavelength excitation resolution, we find that the holes can be excited efficiently at the edge of the hole and that the response becomes stronger in the near-infrared part of the spectrum for larger holes. Using finite-difference time-domain simulations, we characterize the resonant modes inside the holes. We measure the angle-resolved cathodoluminescence response and observe strong beaming toward the side of electron beam excitation, complementary to what was shown for nanoparticles. The angular response can be explained by assuming a coherent superposition of radiating dipole moments, where the contribution of in-plane magnetic and electric dipole components increases for larger diameters.
authors.affiliation: Center for Nanophotonics, FOM Institute AMOLF , Science Park 104, 1098XG Amsterdam, The Netherlands.
authors.forename: Toon
authors.initials: T
authors.lastname: Coenen
authors.forename: Albert
authors.initials: A
authors.lastname: Polman