High-order exceptional points of counterpropagating waves in weakly deformed microdisk cavities

Abstract

In a recent publication [Phys. Rev. A 98, 023851 (2018)] the authors reported on a systematic approach based on perturbation theory to generate non-Hermitian degeneracies, so-called exceptional points, in weakly deformed microdisk cavities by coupling modes of different angular momentum. In the present paper we extent this approach to fully asymmetric boundary deformations. This allows us to increase the order of the exceptional point and create modes with interesting angular momentum patterns where a nonuniform clockwise and counterclockwise propagation is present. Furthermore, we combine the perturbation theory of weakly deformed microdisks with the coupled-mode theory to explain possible measurements of transmission and reflection spectra via a waveguide attached to the cavity.