Fluorescence Lifetime and Blinking of Individual Semiconductor Nanocrystals on Graphene
Résumé
We report on the optical and electrical excitation of the modes of a “hybrid” waveguide consisting of a single organic nanofiber on a thin gold film. In the first set of experiments, light is used to excite the photoluminescence of an organic nanofiber on a thin gold film and the resulting emission is analyzed using Fourier-space leakage radiation microscopy. Two guided modes and the dispersion relations of this hybrid waveguide are thus determined. From numerical calculations, both a fundamental and excited mode of mixed photonic–plasmonic character are identified. In a second experiment, a local electrical nanosource of surface plasmon polaritons (SPPs) is coupled to the hybrid waveguide. The SPP nanosource consists of the inelastic electron tunnel current between the tip of a scanning tunneling microscope (STM) and the gold film. We show that the electrically excited SPPs couple to the fundamental mode and that the coupling efficiency is highest when the SPP nanosource is aligned with the nanofiber axis. Moreover, the electrically excited SPPs strongly scatter into out-of-plane light at the nanofiber end. This light from scattered SPPs measured in the substrate is phase shifted by about π with respect to the direct light emission from beneath the STM tip. These experiments lead to a better understanding of the processes that must be optimized in order to exploit such hybrid waveguide structures.
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