Strong coupling with directional absorption features of Ag@Au hollow nanoshell/J-aggregate heterostructures

Abstract

Abstract Tunable plasmon-exciton coupling is demonstrated at room temperature in hybrid systems consisting of Ag@Au hollow nanoshells (HNSs) and J-aggregates. The strong coupling depends on the exciton binding energy and the localized surface plasmon resonance strength, which can be tuned by changing the thickness of the Ag@Au HNS. An evident anticrossing dispersion curve in the coupled energy diagram of the hybrid system was observed based on the absorption spectra obtained at room temperature. In this paper, strong coupling was observed twice (first at lower wavelength and then also at a higher wavelength) via a single preparation process of the Ag@Au HNS system. The first Rabi splitting energy (ħΩ) is 225 meV. Then, the extinction spectra of the bare Ag@Au HNS and the Ag@Au HNS-J-aggregate hybrid system were reproduced by numerical simulations using the finite-difference time domain method, which were in good agreement with the experimental observations. We attributed the strong coupling of the new shell hybrid system to the reduced local surface plasmon (LSP) mode volume of the Ag@Au HNS. This volume is about 1021.6 nm3. The features of the Ag@Au HNS nanostructure with a small LSP mode volume enabled strong light-matter interactions to be achieved in single open plasmonic nanocavities. These findings may pave the way toward nanophotonic devices operating at room temperature.