Control of Förster energy transfer in the vicinity of metallic surfaces and hyperbolic metamaterials

Optical cavities, plasmonic structures, photonic band crystals and interfaces, as well as, generally speaking, any photonic media with homogeneous or spatially inhomogeneous dielectric permittivity (including metamaterials) have local densities of photonic states, which are different from that in vacuum. These modified density of states environments are known to control both the rate and the angular distribution of spontaneous emission. In the present study, we question whether the proximity to metallic and metamaterial surfaces can affect other physical phenomena of fundamental and practical importance. We show that the same substrates and the same nonlocal dielectric environments that boost spontaneous emission, also inhibit Förster energy transfer between donor and acceptor molecules doped into a thin polymeric film. This finding correlates with the fact that in dielectric media, the rate of spontaneous emission is proportional to the index of refraction n, while the rate of the donor-acceptor energy transfer (in solid solutions with a random distribution of acceptors) is proportional to n(-1.5). This heuristic correspondence suggests that other classical and quantum phenomena, which in regular dielectric media depend on n, can also be controlled with custom-tailored metamaterials, plasmonic structures, and cavities.

Controlling spontaneous emission with metamaterials

We have observed, in metamaterial with hyperbolic dispersion (an array of silver nanowires in alumina membrane), a sixfold reduction of the emission lifetime of dye deposited onto the metamaterial's surface. This serves as evidence of an anomalously high density of photonic states in hyperbolic metamaterials, demonstrates the feasibility of an earlier-predicted single-photon gun, and paves the road for the use of metamaterials in quantum optics.

Influence of doping rate in Er3+:ZnO films on emission characteristics

High-quality Er(3+):ZnO films were grown by the pulsed-laser deposition technique for 0.5 and 2 wt. % Er doping. Two peaks were observed at approximately 1.54 microm in the photoluminescence spectra of samples with 2 wt. % doping contrary to only one peak in the 0.5 wt. % doped sample. Both peaks were found to be strongly temperature dependent. The microscopic studies clearly illustrate that the appearance of the additional peak is attributed to the environment of Er(3+) ions in the form of ErO(6) clusters, which are optically active centers in the ZnO matrix. These results are very important for designing waveguides for telecommunications.