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

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.