Distinguishing the Topological Zero Mode and Tamm Mode in a Microwave Waveguide Array

• Published in: Annalen der Physik Vol. 531; no. 12
• Main Authors: Chen, Tao, Yu, Ye, Song, Yiwen, Yu, Dong, Ye, Hongmei, Xie, Jingya, Shen, Xiaopeng, Pan, Yiming, Cheng, Qingqing
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.12.2019
• Subjects: Arrays; Microwave photonics; Su–Schrieffer–Heeger (SSH) model; Tamm mode; Topology; waveguide array; Waveguides; zero mode
• ISSN: 0003-3804; 1521-3889
• DOI: 10.1002/andp.201900347

The Su–Schrieffer–Heeger (SSH) model has been the subject of extensive experimental research in the context of topological photonics. Ideally, the on‐site potential and hopping strength are sufficiently accurate for implementation in photonic coupled waveguide arrays. Here, two localized edge modes, the topological zero mode and trivial Tamm mode, are proposed and demonstrated in the modified SSH model using a microwave photonic waveguide array. The system used is composed of an array of evanescently coupled ultrathin corrugated metallic “H‐bar” waveguides. Furthermore, the differences between the zero mode and Tamm mode are clearly demonstrated by microwave near‐field experiments on the coupling behavior along the propagation direction for 40 cm at the excitation frequency of 17 GHz. These findings should deepen the understanding of localized edge mode confinement mechanisms, both in coupled waveguide array systems and other topological or quantum systems. Two localized edge modes, the topological zero mode and trivial Tamm mode, are experimentally demonstrated and differentiated in the modified Su–Schrieffer–Heeger (SSH) model using a microwave waveguide array. The findings can inspire the investigation of mode isolation in photonic waveguide arrays, which may provide a new approach to eliminate the effects of disorder and perturbation in future photonic integration.