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O: Fachverband Oberflächenphysik
O 66: Plasmonics and nanooptics: Applications and other aspects II
O 66.7: Talk
Wednesday, March 14, 2018, 16:45–17:00, MA 041
Geometry optimizaton of optical cavities and plasmonic resonators using quasinormal modes — •Philip Kristensen1 and Kurt Busch1,2 — 1Institut für Physik - Humboldt-Universität zu Berlin, 12489 Berlin. — 2Max-Born-Institut, 12489 Berlin.
Optical cavity modes and localized surface plasmon polaritons can be conveniently modeled by so-called quasinormal modes (QNMs), defined as the source free solutions to Maxwell’s equations with the additional requirement of a radiation condition. The QNMs capture most - if not all - the properties typically expected from open electromagnetic resonators. In particular, the radiative loss and material absorption result in complex resonance frequencies, from which the quality factors Q can be calculated directly. From a modeling perspective, one can use perturbation theory with QNMs to estimate the change in resonance frequency due to small changes in the material making up the resonator. In this work, we present a geometry optimization algorithm for controlled tuning of electromagnetic resonators. At each step of the algorithm, we use QNM perturbation theory to calculate the optimum variational change in the resonator boundary required to iteratively shift the complex resonance frequency towards a desired value. This approach alleviates the need for extensive variational testing at each iteration step and provides a stable and efficient overall improvement of the optimization metric. The resulting resonators show interesting and non-trivial organic shapes and support QNMs with optimized parameters, such as increased Q factors.