Direct extraction of topological Zak phase with the synthetic dimension

This paper presents an experimental method for directly extracting the topological Zak phase from the bulk band structures of a Su-Schrieffer-Heeger (SSH) model in a synthetic frequency dimension. Using bichromatically driven rings, the authors construct synthetic SSH lattices in the frequency axis of light, controlling coupling strengths between supermodes. Transmission spectra measurements reveal a strong contrast between trivial and non-trivial topological phases, with the Zak phase encoded in the bulk band structures. The method is demonstrated using a fiber-based modulated ring platform and telecom wavelength laser, extracting Zak phase values consistent with theoretical predictions. The approach is potentially extendable to higher dimensions and has applications in optical communications.

Guangzhen Li, Luojia Wang, Rui Ye, Yuanlin Zheng, Da-Wei Wang, Xiong-Jun Liu, Avik Dutt, Luqi Yuan, Xianfeng Chen