Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore.
State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027, China.
Nat Commun. 2016 May 20;7:11619. doi: 10.1038/ncomms11619.
Topological photonic states, inspired by robust chiral edge states in topological insulators, have recently been demonstrated in a few photonic systems, including an array of coupled on-chip ring resonators at communication wavelengths. However, the intrinsic difference between electrons and photons determines that the 'topological protection' in time-reversal-invariant photonic systems does not share the same robustness as its counterpart in electronic topological insulators. Here in a designer surface plasmon platform consisting of tunable metallic sub-wavelength structures, we construct photonic topological edge states and probe their robustness against a variety of defect classes, including some common time-reversal-invariant photonic defects that can break the topological protection, but do not exist in electronic topological insulators. This is also an experimental realization of anomalous Floquet topological edge states, whose topological phase cannot be predicted by the usual Chern number topological invariants.
拓扑光子态受拓扑绝缘体中稳定的手性边缘态启发，已在一些光子系统中得到验证，包括在通讯波段的耦合片上环形谐振器阵列。然而，电子与光子之间的固有差异决定了时间反演不变光子系统中的“拓扑保护”与电子拓扑绝缘体中的拓扑保护并不完全相同。在本研究中，我们构建了一个由可调谐金属亚波长结构组成的表面等离激元平台，在该平台中构造了光子拓扑边缘态，并研究了它们对多种缺陷类型的鲁棒性，包括一些常见的时间反演不变光子缺陷，这些缺陷会破坏拓扑保护，但在电子拓扑绝缘体中并不存在。这也是反常 Floquet 拓扑边缘态的实验实现，其拓扑相不能用通常的陈数拓扑不变量来预测。
