Surface plasmons excited by the photoluminescence of organic nanofibers in hybrid plasmonic systems

Recent research on hybrid plasmonic systems has shown the existence of a loss channel for energy transfer between organic materials and plasmonic/metallic structured substrates. This work focuses on the exciton-plasmon coupling between para-Hexaphenylene (p-6P) organic nanofibers (ONFs) and surface plasmon polaritons (SPPs) in organic/dielectric/metal systems. We have transferred the organic p-6P nanofibers onto a thin silver film covered with a dielectric (silicon dioxide) spacer layer with varying thicknesses. Coupling is investigated by two-photon fluorescence-lifetime imaging microscopy (FLIM) and leakage radiation spectroscopy (LRS). Two-photon excitation allows us to excite the ONFs with near-infrared light and simultaneously avoids direct SPP excitation on the metal layer. We observe a strong dependence of fluorescence lifetime on the type of underlying substrate and on the morphology of the fibers. The experimental findings are complemented via finite-difference time-domain (FDTD) modeling. The presented results lead to a better understanding and control of hybrid-mode systems, which are crucial elements in future low-loss energy transfer devices.