Large single-molecule fluorescence enhancement produced by a bowtie nanoantenna

摘要

Owing to the size mismatch between light and nanoscaleobjects such as single molecules, it is important to be able tocontrol light-molecule interactions1-4. Plasmonic nanoantennascreate highly enhanced local fields when pumped resonantly,leading to increased Raman scatterings, but whether fluores-cence enhancement occurs depends upon a variety of factors.Although sharp metal tips6 and colloide7,8 can enhance fluores-cence, the highly enhanced optical fields of lithographicallyfabricated bowtie nanoantennas9 provide a structrues that ismore controllable and amenable to integration. Using goldbowties, we observe enhancements of a single molecule'sfluorescence up to a factor of 1,340, ten times higher thanreported previously7,8,10-22. Electromagnetic simulations revealthat this is a result of greatly enhanced absorption and anincreased radiative emission rate, leading to enhancement ofthe intrinsic quantum efficiency by an estimated factor ofnine, despite additional non-radiative ohmk effects. Bowtienanoantennas thus show great potential for high-contrastselection of single nanoemitters.