Probing Phase Transition of Band Topology via Radiation Topology

• Chang-Yin Ji, Wenze Lan, Peng Fu, Gang Wang, Changzhi Gu, Yeliang Wang, Jiafang Li, Yugui Yao, and Baoli Liu
• received 07/17/2023; accepted 01/09/2024; posted 01/09/2024; Doc. ID 500575
• Abstract: Topological photonics has received extensive attention from researchers because it provides brand new physical principles to manipulate light. Band topology is characterized using the Berry phase defined by Bloch states. Until now, the scheme for experimentally probing the topological phase transition of band topology has always been relatively lacking in topological physics. Moreover, radiation topology can be aroused by the far-field polarization singularities of Bloch states, which is described by the Stokes phase. Although such two types of topologies are both related to Bloch states on the band structures, it is rather surprising that their development is almost independent. Here, in optical analogs of the quantum spin Hall effects (QSHEs) and Su-Schrieffer-Heeger model, we reveal the correlation between the phase transition of band topology and radiation topology and then demonstrate that the radiation topology can be employed to study the band topological transition. We experimentally demonstrate such an intriguing phenomenon in optical analogs of QSHEs. Our findings not only provide an insightful understanding of band topology and radiation topology, but also can serve as a novel route to manipulate the light.