Unidirectional frequency conversion of surface plasmon polaritons on metal nanowires

Hybrid nanoplasmonics is one of the most promising branch of nanophotonics which aims, in particular, to control the energy transfer between donor and acceptor nano-emitters via surface plasmons. Recently, an approach of nano-emitters positioning was introduced. It is based on two-photon polymerization of a photosensitive material which contains quantum dots as nano-emitters. This technique allowed for the integration of green quantum dots on plasmonic silver nanowires. In this article, we report on the use of this approach for integrating both green and red quantum dots on silver nanowires. The coupling between nano-emitters and propagating surface plasmons that are supported by the silver nanowires is reported and observed through their scattering at the nanowire ends. For both colors, a parametric study of the distance between the quantum dots and the nanowire extremity shows that precise control of the position of the launching sites enables control of light intensity at the wire end, through surface plasmon propagation length. More interestingly, by integrating two kinds of quantum dots on the same nanowire, we realized an efficient donor-acceptor hybrid nano-system, where green surface plasmons polaritons (from donors) are transformed into red plasmons (from acceptors) at controlled sites of the plasmonic guides, as a result of a frequency conversion of the plasmons polaritons.