Strong coupling and ultrafast dynamics in organic semiconductor/metal hybrid nanostructures

Abstract

Active plasmonics, as an important branch of Plasmonics, is growing rapidly over the last decades. The main principle of active plasmonics is to combine surface plasmon polaritons (SPPs) with ‘active’ materials to com-penstate intrinsic weak optical nonlinearities and short propagation lengths of SPPs, so that external manipula-tion and coherent control of SPPs can be realized. Here, we give a brief review of the studies in the area of active plasmonics. In particular, we focus on hybrid J-aggregate/metal nanostructures consisting of J-aggregate excitons and surface plasmon polaritons supported by metallic nanostructures. Two experimental methods: chrip-compensated spectral interferometry and nonlinear pump-probe spectroscopy are introduced. The strong coupling between J-aggregate excitons and SPPs is studied in details by probing both the static optical properties and ultrasfast dynamics of the strongly coupled X-SPP systems. The results reveal that two different energy transfer channels: a coherent resonant dipole-dipole interaction and an incoherent exchange of photons, are coexisting in the hybrid system. Coherent energy exchange, that is, Rabi oscillations between the excitonic and the SPP systems in real time are also investigated. It is found that coherent X-SPP population transfer induces transient oscillations in exciton density, leading to a periodic modulation of the normal mode splitting and thus optical nonlinearity on a 10 fs timescale.