Reduction of the fluorescence lifetime of quantum dots in presence of plasmonic nanostructures

Developing a single photon source in the near infrared spectrum for optical fibre communications implies the control of the spontaneous emission of quantum dots. In this paper we show that the fluorescence lifetime of lead sulphide quantum dots can be drastically decreased due to the presence of plasmonic nanostructures specially designed to confine the electromagnetic field to which the emitted photons could decay at lambda=1550nm. To demonstrate this, we first measured the fluorescence lifetime of colloidal quantum dots in toluene solution and took this as a reference measurement. Then, we compared this value with the fluorescence lifetime of quantum dots in two different plasmonic nanostructures. The measurement of lifetime was made using the Time-Correlated Single Photon Counting technique. We obtained for the quantum dots in solution a fluorescence lifetime of 0.98084 mu s and for the quantum dots in the nanostructures, fluorescence lifetimes of 0.06227 mu s and 0.11789 mu s. We also numerically calculated the distribution of the electromagnetic field near the plasmonic nanostructures. These results demonstrate that the plasmonic nanostructures modified the fluorescence lifetime of the quantum dots, and that these plasmonic nanostructures with the lead sulphide quantum dots could work as a single photon source that could be integrated in a photonic circuit for infrared optical fibre communications.