Control of the two-photon fluorescence of quantum dots coupled to silver nanowires

Plasmon-based fluorescence modulation has led to important advances in various fields and has paved the way toward promising scientific research aimed at enabling new applications. However, the modulation of fluorescence properties based on both localized surface plasmon (LSP) and cavity modes of propagating surface plasmon polaritons (SPPs) are rarely reported. Here, we raster scanned a hybrid nanowire (HNW) with quantum dots (QDs) adsorbed onto a Ag nanowire (NW) and obtained two-photon fluorescence (TPF) maps of the intensity and decay rate. The spatial distributions of the intensity and decay rate strongly depend on the Fabry-Pérot (FP) cavity modes of the SPPs, the LSP mode launched by the incident laser and the excitation energy of the QDs. A double exponential decay process was observed, which is attributed to different decay channels through the LSP and cavity modes. The experimental results are explained using numerical simulations. This work shows that many physical parameters, such as the polarization of the incident beam and the geometry of the Ag NW, can modulate the fluorescence properties of the QDs, which has potential applications in many important fields.