title: Ultrasmall mode volume plasmonic nanodisk resonators.
abstract: We study the resonant modes of nanoscale disk resonators sustaining metal-insulator-metal (MIM) plasmons and demonstrate the versatility of these cavities to achieve ultrasmall cavity mode volume. Ag/SiO2/Ag MIM structures were made by thin-film deposition and focused ion beam milling with cavity diameters that ranged from d = 65-2000 nm. High-resolution two-dimensional cavity-mode field distributions were determined using cathodoluminescence imaging spectroscopy and are in good agreement with boundary element calculations. For the smallest cavities (d = 65-140 nm), the lowest order mode (m = 1, n = 1) is observed in the visible spectral range. This mode is of similar nature as the one in plasmonic particle dimers, establishing a natural connection between localized and traveling plasmon cavities. A cavity quality factor of Q = 16 is observed for the 105 nm diameter cavity, accompanied by a mode volume as small as 0.00033lamda(0)(3). The corresponding Purcell factor is 900, making these ultrasmall disk resonators ideal candidates for studies of enhanced spontaneous emission and lasing.
authors.affiliation: Center for Nanophotonics, FOM-Institute AMOLF, Sciencepark 113, Amsterdam, The Netherlands. kuttge@amolf.nl
authors.forename: Martin
authors.initials: M
authors.lastname: Kuttge
authors.forename: F Javier
authors.initials: FJ
authors.lastname: García de Abajo
authors.forename: Albert
authors.initials: A
authors.lastname: Polman
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000295:instrumentation*; D010316:Particle Size; D020349:Surface Plasmon Resonance / Q000295:instrumentation*; D014159:Transducers