Abstract
The nanofocusing performance of hourglass plasmonic waveguides is studied analytically and numerically. Nonlocal effects in the linearly tapered metal-air-metal stack that makes up the device are taken into account within a hydrodynamical approach. Using this hourglass waveguide as a model structure, we show that spatial dispersion drastically modifies the propagation of surface plasmons in metal voids, such as those generated between touching particles. Specifically, we investigate how nonlocal corrections limit the enormous field enhancements predicted by local electromagnetic treatments of geometric singularities. Finally, our results also indicate the emergence of nonlocality assisted tunnelling of plasmonic modes across hourglass contacts as thick as 0.5 nm.
Highlights
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2. Title: Nonlocal propagation and tunnelling of surface plasmons in metallic hourglass waveguides Author(s): Wiener, Aeneas; Fernandez-Dominguez, Antonio I.; Pendry, J
Summary
The report outlines the PI’s month of agreed time in the USA (talks at Berkeley, UCSD, and several conferences) and collaborations with US researchers David Smith and Xiang Zhang. The main advance of this year’s research is extend the analytical work in transformation optics (relating complex systems to simpler systems with the same spectral properties) to singular 3d objects such as touching spheres, which gives rise to strong enhancement of local fields and nonlinear phenomena, opening the possibility of eg single-molecule detectors. The analytic solutions of these systems facilitate a quantitative understanding of the systems and qualitative appreciation of how the enhancement comes about. They used this technique to calculate the Van der Waals forces between two nearly-touching nanospheres. A concerning effect is the nonlocality of the dielectric response, in which charge is slightly spread through a material rather than accumulating purely on the surface; the team arrived at a simple approximation and helps increase the understanding of subnanometre regime in optics
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