Dresden 2020 – scientific programme
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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 7: Whispering-Gallery-Mode Resonators
KFM 7.4: Talk
Tuesday, March 17, 2020, 15:00–15:20, TOE 317
Nonhermitian defect states from lifetime differences — •Marti Bosch1,2, Simon Malzard2,3, Martina Hentschel1, and Henning Schomerus2 — 1TU Ilmenau, Ilmenau, Deutschland — 2Lancaster University, Lancaster, UK — 3Imperial College London, London, UK
Nonhermitian systems provide new avenues to create topological defect states. An unresolved general question is how much the formation of these states depends on asymmetric backscattering, be it nonreciprocal as in the nonhermitian skin effect or reciprocal as encountered between the internal states of asymmetric microresonators. Here, we demonstrate in a concrete, practically accessible setting of a lossy coupled-resonator optical waveguide that nonhermitian defect states can exist in open optical systems due to lifetime differences, without the need for asymmetric backscattering within or between the individual resonators. We apply our findings to a finite system of coupled circular resonators perturbed by nanoparticles, following the concept of creating an interface by inverting the position of the nanoparticles in half of the chain. We compare a coupled-mode tightbinding approximation to full-wave numerical simulations, showing that spectrally isolated defect states can indeed be implemented in this simple nonhermitian photonic device.