Dynamically encircling an exceptional point (EP) in parity-time (PT) symmetric waveguide systems exhibits interesting chiral dynamics that can be applied to asymmetric mode switching for symmetric and anti-symmetric modes. The counterpart symmetry-broken modes (i.e., each eigenmode is localized in one waveguide only), which are more useful for applications such as on-chip optical signal processing, exhibit only non-chiral dynamics and therefore cannot be used for asymmetric mode switching. Here, we solve this problem by resorting to anti-parity-time (anti-PT) symmetric systems and utilizing their unique topological structure, which is very different from that of PT-symmetric systems. We find that the dynamical encircling of an EP in anti-PT-symmetric systems with the starting point in the PT-broken phase results in chiral dynamics. As a result, symmetry-broken modes can be used for asymmetric mode switching, which is a phenomenon and application unique to anti-PT-symmetric systems. We perform experiments to demonstrate the new wave-manipulation scheme, which may pave the way towards designing on-chip optical systems with novel functionalities.

在奇偶时间（PT）对称波导系统中动态环绕例外点（EP）表现出有趣的手性动力学，可以将其应用于对称和反对称模式的非对称模式切换。对应的对称中断模式（即，每个本征模式仅位于一个波导中），这对于诸如片上光信号处理之类的应用更为有用，仅表现出非手性动力学，因此不能用于非对称模式切换。在这里，我们诉诸反奇偶时间（抗解决这个问题PT）对称系统，并利用其独特的拓扑结构，这是从非常不同的PT -对称系统。我们发现EP在反PT中的动态包围以PT断裂相为起点的对称系统导致手性动力学。结果，可以将对称破坏模式用于非对称模式切换，这是反PT对称系统独有的现象和应用。我们进行实验以演示新的波处理方案，这可能为设计具有新颖功能的片上光学系统铺平道路。