Scanning planar Yagi-Uda antenna for fluorescence detection
Authors: Soldani N., Rabbany Esfahany E., Druzhinin S., Gregor S., Müller J., Sledz F., Flatae A.M., Butz B., Schönherr H., Markesevic N., Agio M.
Autors Affiliation: Laboratory of Nano-Optics, University of Siegen, Siegen 57072, Germany; Research Center for Micro and Nano-Chemistry and Engineering (Cμ), Siegen 57076, Germany; Physical Chemistry I, University of Siegen, Siegen 57076, Germany; Micro- and Nanoanalytics Group, University of Siegen, Siegen 57076, Germany; Currently with Nanoscience Center, University of Jyväskylä, Jyväskylä 40014, Finland; National Institute of Optics (INO), National Research Council (CNR), Florence 50125, Italy
Abstract: An effective approach to improve the detection efficiency of nanoscale light sources relies on a planar antenna configuration, which beams the emitted light into a narrow cone. Planar antennas operate like optical Yagi-Uda antennas, where reflector and director elements are made of metal films. Here we introduce and investigate, both theoretically and experimentally, a scanning implementation of a planar antenna. Using a small ensemble of molecules contained in fluorescent nanobeads placed in the antenna, we independently address the intensity, radiation pattern, and decay rate as a function of distance between a flat-tip scanning gold wire (reflector) and a thin gold film coated on a glass coverslip (director). The scanning planar antenna changes the radiation pattern of a single fluorescent bead, and it beams light into a narrow cone down to angles of 45∘ (full width at half maximum). Moreover, the collected signal compared to the case of a glass coverslip is larger than a factor of three, which is mainly due to the excitation enhancement. These results offer a better understanding of the modification of light–matter interaction by planar antennas, and they hold promise for applications such as sensing, imaging, and diagnostics.
Journal/Review: JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B: OPTICAL PHYSICS
Volume: 38 Pages from: 2528 to: 2535