title: Observation of Mode Splitting in Photoluminescence of Individual Plasmonic Nanoparticles Strongly Coupled to Molecular Excitons.
abstract: Plasmon-exciton interactions are important for many prominent spectroscopic applications such as surface-enhanced Raman scattering, plasmon-mediated fluorescence, nanoscale lasing, and strong coupling. The case of strong coupling is analogous to quantum optical effects studied in solid state and atomic systems previously. In plasmonics, similar observations have been almost exclusively made in elastic scattering experiments; however, the interpretation of these experiments is often cumbersome. Here, we demonstrate mode splitting not only in scattering, but also in photoluminescence of individual hybrid nanosystems, which manifests a direct proof of strong coupling in plasmon-exciton nanoparticles. We achieved these results due to saturation of the mode volume with molecular J-aggregates, which resulted in splitting up to 400 meV, that is, ∼20% of the resonance energy. We analyzed the correlation between scattering and photoluminescence and found that splitting in photoluminescence is considerably less than that in scattering. Moreover, we found that splitting in both photoluminescence and scattering signals increased upon cooling to cryogenic temperatures. These findings improve our understanding of strong coupling phenomena in plasmonics.
authors.affiliation: Department of Physics, Chalmers University of Technology , 412 96 Göteborg, Sweden.
authors.forename: Martin
authors.initials: M
authors.lastname: Wersäll
authors.affiliation: Department of Physics, Chalmers University of Technology , 412 96 Göteborg, Sweden.
authors.forename: Jorge
authors.initials: J
authors.lastname: Cuadra
authors.affiliation: Department of Physics, Chalmers University of Technology , 412 96 Göteborg, Sweden.|Centre of New Technologies, University of Warsaw , Banacha 2c, 02-097 Warsaw, Poland.
authors.forename: Tomasz J
authors.identifier: 0000-0003-2535-4174
authors.initials: TJ
authors.lastname: Antosiewicz
authors.affiliation: Department of Astronautical Engineering, University of Turkish Aeronautical Association , 06790 Ankara, Turkey.
authors.forename: Sinan
authors.initials: S
authors.lastname: Balci
authors.affiliation: Department of Physics, Chalmers University of Technology , 412 96 Göteborg, Sweden.
authors.forename: Timur
authors.identifier: 0000-0002-4266-3721
authors.initials: T
authors.lastname: Shegai
mesh_terms: D005456:Fluorescent Dyes / Q000737:chemistry*; D049449:Luminescence; D053768:Metal Nanoparticles / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D055585:Physical Phenomena; D012834:Silver / Q000737:chemistry*; D020349:Surface Plasmon Resonance
chemical_list: D005456:Fluorescent Dyes; D012834:Silver
keywords: Rabi splitting; Strong coupling; photoluminescence; plasmon−exciton interactions; plexciton