High-order exceptional points in non-Hermitian Moiré lattices
Yan-Rong Zhang1, Ze-Zheng Zhang1, Jia-Qi Yuan1, Ming Kang2(), Jing Chen1,3()
1. MOE Key Laboratory of Weak-Light Nonlinear Photonics, School of Physics, Nankai University, Tianjin 300071, China 2. College of Physics and Materials Science, Tianjin Normal University, Tianjin 300387, China 3. Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
This study proposes an approach to generate high-order exceptional points (EPs) in non-Hermitian systems. A system comprising a homogenous waveguide is considered wherein the imaginary part of the refractive index is modulated using a one-dimensional Moiré profile. This gain-loss modulation couples different lossless waveguide modes, and these hybrid modes can be modeled using a non-Hermitian matrix with complex off-diagonal elements. Results indicate that third-order EPs can be produced by the coalescence of two second-order EPs. Then, the necessary requirements are analyzed using coupled-wave equations and the physical effects of the singularities are discussed.
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