Zhang Yan-Rong, Zhang Ze-Zheng, Yuan Jia-Qi, Wang Wei, Wang Lu-Qi, Li Zheng-Xian, Xue Rui-Dong, Chen Jing
Opt Express. 2018 Oct 15;26(21):27141-27152. doi: 10.1364/OE.26.027141.
The coupling strength between two parity-time (PT) symmetric resonators determines whether the PT phase is broken or not. Here we investigate the scenario that two optical waveguides are spatially curved so that they switch periodically between unbroken and broken PT phases. We show that the existence of locally broken PT phase does not necessarily render a broken phase to waves propagating inside. Criteria are proposed to characterize the collective dynamics of wave near the Brillouin zone (BZ) edge, toward the cases of a totally broken phase, a partially broken phase, or a totally unbroken phase. We also discuss the characteristics of two special kinds of exceptional points (EPs) at the BZ edge, and show that their field patterns are displaced by half a period with each other. Full-wave numerical simulation proves our analysis. Potential applications especially these associated with EPs are discussed. This study helps us to understand how the locally PT-symmetric related eigenstate influences the globally collective dynamics of wave in spatially periodic configuration.
两个宇称时间（PT）对称谐振器之间的耦合强度决定了PT相是否被破坏。在此，我们研究了两个光波导在空间上弯曲，从而使其在未破坏和破坏的PT相之间周期性切换的情况。我们表明，局部破坏的PT相的存在并不一定会使在其内部传播的波呈现破坏相。提出了一些准则来表征靠近布里渊区（BZ）边缘的波的集体动力学，针对完全破坏相、部分破坏相或完全未破坏相的情况。我们还讨论了BZ边缘处两种特殊类型的例外点（EPs）的特性，并表明它们的场模式彼此相差半个周期。全波数值模拟证实了我们的分析。讨论了潜在的应用，特别是与EPs相关的应用。这项研究有助于我们理解局部PT对称相关本征态如何影响空间周期性配置中波的全局集体动力学。
