Feng Fanghu, Wang Neng, Wang Guo Ping
China State Key Laboratory of Radio Frequency Heterogeneous Integration, College of electronics and Information Engineering, Shenzhen University, Shenzhen, 518060, China.
Sci Rep. 2025 May 10;15(1):16342. doi: 10.1038/s41598-025-00998-0.
This study theoretically investigates the realization of exceptional points (EPs) in space-time invariant Lorentz dispersive media with uniform loss, which contrasts sharply with conventional approaches that rely on spatial or temporal differential losses. Using the derived full and reduced Hamiltonians, we reveal that uniform loss in Lorentz dispersive media not only introduces attenuation to the eigenmodes of the lossless medium but also enables two distinct types of non-Hermitian couplings: reciprocal and non-reciprocal. Both coupling mechanisms independently contribute to the emergence of EPs. The EPs manifest as exceptional lines (ELs) in the parameter space, and a fourth-order EP (EP4) is formed when three ELs intersect at a single point. Remarkably, at the EP4, all eigenmodes exhibit maximum optical chirality density, presenting potential applications such as chiral sorting. Our findings provide valuable insights into the mechanisms underpinning the formation of EPs.
本研究从理论上探究了具有均匀损耗的时空不变洛伦兹色散介质中例外点（EPs）的实现情况，这与依赖空间或时间微分损耗的传统方法形成鲜明对比。利用推导得到的完整和简化哈密顿量，我们揭示出洛伦兹色散介质中的均匀损耗不仅会给无损介质的本征模引入衰减，还能实现两种不同类型的非厄米耦合：互易和非互易耦合。这两种耦合机制都独立地促成了例外点的出现。例外点在参数空间中表现为例外线（ELs），当三条例外线相交于一点时会形成一个四阶例外点（EP4）。值得注意的是，在EP4处，所有本征模都表现出最大的光学手性密度，展现出诸如手性分选等潜在应用。我们的研究结果为理解例外点形成的机制提供了有价值的见解。
