Time-resolved surface plasmon polariton coupled exciton and biexciton emission

Abstract

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.

Exciton−Plasmon Interactions in Metal−Semiconductor Nanostructures

“…Therefore, the combination of the two material systems can provide attractive opportunities to modify and design specific optical properties and to observe new phenomena that are based on exciton-plasmon interactions (Figure 2a). Recent examples have been ubiquitous and can be roughly divided into three categories, which are modification and design of absorption and emission properties, energy transfer between excitonic and plasmonic systems, [41][42][43][44][45][46][47][48][49][50][51][52] and strong coupling with coherent excitonplasmon interactions. 53,54 This partitioning should not be taken too rigorously because many of the observed phenomena are simply different facets of the same underlying physical process.…”

“…49,50 Semiconductor nanocrystals are particularly well-suited for this task due to their high optical gain that arises from multiexcitons that can couple to surface plasmon polaritons. 46 When nanocrystals couple with metallic nanorods (Figure 4b), the energy is guided, locally concentrated, and released by SPs. 44,45 In such nanoscale energy transport, the transferred energy maintains the quantized character of the excitonic source and can lead to single SP excitations.…”

“…Therefore, the combination of the two material systems can provide attractive opportunities to modify and design specific optical properties and to observe new phenomena that are based on exciton−plasmon interactions (Figure a). Recent examples have been ubiquitous and can be roughly divided into three categories, which are modification and design of absorption and emission properties, − energy transfer between excitonic and plasmonic systems, − and strong coupling with coherent exciton−plasmon interactions. , This partitioning should not be taken too rigorously because many of the observed phenomena are simply different facets of the same underlying physical process. Besides a fundamental interest in the properties of exciton−plasmon interactions, metal−semiconductor nanostructures have also attracted attention for their potential use in applications including optical sensing, light emitters, photovoltaic systems, and quantum information and communication applications.…”

“…The possibility of exchanging energy between the excitonic and the plasmonic system has been exploited in many situations, − including SP amplification and lasing. − In general, when an optical dipole is located in the vicinity of a metal structure and spectrally resonant with SPs, energy transfer between the two systems occurs. In the case of weak exciton−plasmon coupling, the energy transfer can be considered unidirectional.…”

“…In a simple model system consisting of NCs in the proximity of a thin metal film, energy transfer occurs from the excitonic system to surface plasmon polaritons (SPPs) that propagate on the metal surface. The coupled energy can then be released into photons and generate surface plasmon polariton coupled emission, as schematically shown in Figure a, , or it can be used to amplify SPPs. , Semiconductor nanocrystals are particularly well-suited for this task due to their high optical gain that arises from multiexcitons that can couple to surface plasmon polaritons . When nanocrystals couple with metallic nanorods (Figure b), the energy is guided, locally concentrated, and released by SPs. , In such nanoscale energy transport, the transferred energy maintains the quantized character of the excitonic source and can lead to single SP excitations …”