Time-resolved surface plasmon polariton coupled exciton and biexciton emission

We discuss the coupling between optically excited semiconductor nanocrystals (NC) and thin metal films in both the single and multi-exciton regime. Using time-resolved photoluminescence spectroscopy, we determine the decay dynamics of free space and surface plasmon polariton (SPP) coupled emission. The two dynamics are found to be distinctly different at very small NC-metal separations and at photon energies close to the SPP resonance frequency. A comparison with numerical calculations allow us to conclude that the difference in emission dynamics is associated with the different interactions of parallel and perpendicular dipole emitters with lossy surface waves. Experiments at high excitation densities reveal that the coupling to SPPs and lossy surface waves is identical for excitons and biexcitons.