title: Resonant plasmon nanofocusing by closed tapered gaps.
abstract: We study radiation nanofocusing by closed tapered gaps, i.e. metal V-grooves, under normal illumination, and discover that the local field inside a groove can be resonantly enhanced due to interference of counter-propagating gap plasmons. Considering V-grooves milled in gold, we analyze this phenomenon theoretically, deriving an analytic expression for the resonance condition and predicting more than 550-fold intensity enhancements at resonance, and observe it experimentally with two-photon photoluminescence microscopy, demonstrating more than 100-fold intensity enhancements.
authors.affiliation: Department of Physics and Nanotechnology, Aalborg University, Skjernvej 4A, Aalborg Øst, Denmark.
authors.forename: Thomas
authors.initials: T
authors.lastname: Søndergaard
authors.forename: Sergey I
authors.initials: SI
authors.lastname: Bozhevolnyi
authors.forename: Jonas
authors.initials: J
authors.lastname: Beermann
authors.forename: Sergey M
authors.initials: SM
authors.lastname: Novikov
authors.forename: Eloïse
authors.initials: E
authors.lastname: Devaux
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Ebbesen
mesh_terms: D015374:Biosensing Techniques; D003198:Computer Simulation; D004574:Electromagnetic Fields; D006046:Gold / Q000737:chemistry; D008027:Light; D053768:Metal Nanoparticles / Q000737:chemistry; D008853:Microscopy / Q000379:methods; D008855:Microscopy, Electron, Scanning / Q000379:methods; D015233:Models, Statistical; D053758:Nanoparticles; D049329:Nanostructures / Q000737:chemistry; D036103:Nanotechnology / Q000379:methods*; D020349:Surface Plasmon Resonance
chemical_list: D006046:Gold