Intermediate Field Coupling of Single Epitaxial Quantum Dots to Plasmonic Waveguides

Abstract

Key requirements for quantum plasmonic nanocircuits are reliable single-photon sources, high coupling efficiency to the plasmonic structures, and low propagation losses. Self-assembled epitaxially grown GaAs quantum dots are close to ideal as stable, bright, and narrowband single-photon emitters. Likewise, wet-chemically grown monocrystalline silver nanowires are among the best plasmonic waveguides. However, large propagation losses of surface plasmons on the high-index GaAs substrate prevent their direct combination. Here, we show by experiment and simulation that the best overall performance of the quantum plasmonic nanocircuit based on these building blocks is achieved in the intermediate field regime with an additional spacer layer between the quantum dot and the plasmonic waveguide. High-resolution cathodoluminescence measurements allow a precise determination of the coupling distance and support a simple analytical model to explain the overall performance. The coupling efficiency is increased up to four times by standing wave interference near the end of the waveguide.

Integrated Manipulation and Addressing of Spin Defect in Diamond

“…Though shorter than the propagation length with a suspended AgNW, it is enough for the selective optical excitation of NV centers in a diamond. A longer propagation length could be realized by inserting a low-refractive-index layer to increase the distance between diamond and nanowire. , But we should be careful of the NV center excitation efficiency with a large distance. For the distribution of optical excitation perpendicular to the AgNW, a full width at half-maximum (fwhm) of 705 nm is extracted by fitting the cross-section with a Gaussian function, as in the inset of Figure b.…”