Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 40: Focussed session: Coherence and coherent control in nanophotonics and plasmonics I

O 40.2: Topical Talk

Wednesday, March 28, 2012, 11:00–11:30, MA 005

Coherent exciton-plasmon coupling in metal-dye hybrid nanostructures — •Erich Runge — Technische Universität Ilmenau, 98693 Ilmenau, Germany

At nano-structured metal surfaces, light can be localized to spatial regions well below the diffraction limit by the excitation of surface plasmon polaritons (SPPs). A major challenge for future devices employing SPPs is the fact that SPPs travel only over very short distances, since they are strongly damped in the metal. One approach to overcome this problem is to compensate the damping by coupling of the SPPs to active media, e.g., dyes or quantum wells [P. Vasa et al., Phys. Rev. Lett. 110 (2008) 116801].

Based on recent experiments in the Lienau group at Oldenburg University, I discuss in detail the coupling of quantum mechanical excitations in a j-aggregated dye with the SPP excitation at a metal grating [P. Vasa et al., ACS Nano, 4 (2010), pp. 7559]. The strong coupling (energy transfer) of the SPP and the excitonic dye resonance manifests itself as avoided crossing in the dispersion relation. At resonance, the coupled eigenmodes show excitonic as well as plasmonic features. They inherit a ultrafast strongly non-linear response (saturation and induced biexcitonic absorption) from their excitonic parent, i.e., from the organic dye. If the dye is saturated, its excitonic polarizability vanishes and so does its coupling to the plasmon. The hybridization gap in the mixed-mode dispersion relation closes. This allows for reflectivity changes by about 40% on and off in less than a picoseconds, arguably making the sample the fastest switchable metallic mirror ever made.