Double exceptional points in -symmetric structures with an anisotropic layer
Phys. Rev. B 112, 045401 – Published 1 July, 2025
DOI: https://doi.org/10.1103/66qc-hrzr
Abstract
The introduction of anisotropic media into non-Hermitian photonic systems provides novel means for manipulations with their exceptional points (EPs)—the singularities of degenerate eigenfrequencies and eigenmodes. In this paper, we propose a concept of double EPs appearing in the -symmetric three-layer structures with the anisotropic middle layer. This becomes possible when the anisotropic medium optical axis lies out of the layers' plane. We show that the structure possesses two-sided reflectionlessness at the double EPs for one of the polarizations and has minimal transmission for the orthogonal polarization that can be used as a new approach to obtain polarized radiation. We study the dependence of double EPs' position on the system parameters demonstrating double EP stability with respect to the non-Hermiticity level and their tunability with respect to layer thicknesses and the anisotropy level. Moreover, the out-of-plane orientation of the optical axis can be considered as a general method to control positions and the number of EPs in non-Hermitian systems.
