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Channeling light into quantum-scale gaps

Physical Review B - Condensed Matter and Materials Physics

Kekatpure, Rohan D.; Davids, Paul D.

We develop a discrete plasmonic mode-matching technique to investigate the ultimate limits to plasmonic light concentration down to the length scales required for observation of quantum-mechanical phenomena, including plasmon-assisted electron tunneling. Our mode-matching calculations, verified by direct numerical solution of Maxwell's equations, indicate achievable coupling efficiencies of >20% into symmetric bound gap plasmon modes in sub-10-nm gaps. For a given operating wavelength and a choice of material parameters, we demonstrate the existence of a specific width that maximizes enhancement of the electromagnetic field coupled into the gap. More generally, our calculations establish an intuitive and a computationally efficient framework for determining coupling efficiencies in and out of quantum-scale waveguides. © 2011 American Physical Society.

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First-principles full-vectorial eigenfrequency computations for axially symmetric resonators

Journal of Lightwave Technology

Kekatpure, Rohan D.

Starting from the time-harmonic Maxwell's equations in cylindrical coordinates, we derive and solve the finite-difference (FD) eigenvalue equations for determining vector modes of axially symmetric resonator structures such as disks, rings, spheres and toroids. Contrary to the most existing implementations, our FD scheme is readily adapted for both eigenmode and eigenfrequency calculations. An excellent match of the FD solutions with the analytically calculated mode indices of a microsphere resonator provides a numerical confirmation of the mode-solver accuracy. The comparison of the presented FD technique with the finite-element method highlights the relative strengths of both techniques and advances the FD mode-solver as an important tool for cylindrical resonator design. © 2010 IEEE.

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8 Results
8 Results