• Chinese Optics Letters
  • Vol. 19, Issue 4, 042601 (2021)
Ye Yu1, Yiwen Song1, Tao Chen1, Huaiqiang Wang2、*, Songlin Zhuang1, and Qingqing Cheng1、**
Author Affiliations
  • 1School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China
  • 2National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China
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    Floquet topological insulators (FTIs) have been used to study the topological features of a dynamic quantum system within the band structure. However, it is difficult to directly observe the dynamic modulation of band structures in FTIs. Here, we implement the dynamic Su–Schrieffer–Heeger model in periodically curved waveguides to explore new behaviors in FTIs using light field evolutions. Changing the driving frequency produces near-field evolutions of light in the high-frequency curved waveguide array that are equivalent to the behaviors in straight arrays. Furthermore, at modest driving frequencies, the field evolutions in the system show boundary propagation, which are related to topological edge modes. Finally, we believe curved waveguides enable profound possibilities for the further development of Floquet engineering in periodically driven systems, which ranges from condensed matter physics to photonics.

    1. Introduction

    Recently, photonic topological insulators have been cutting-edge research topics in condensed matter physics because of the emergence of topologically protected states located at interfaces[1,2]. Interface states in static topological systems are characterized by their immunity to perturbations, which have given rise to many interesting phenomena and potential applications[16]. The topological characteristics in the dynamics of driven quantum systems provide newly engineered, topologically nontrivial phases that are not accessible in static systems[7]. Therefore, a series of early works developed the notion of a “Floquet topological insulator” (FTI)[8], which can appropriately modulate the drive frequency[7], amplitude[3], and symmetry to engineer the topological features of a band structure[9,10]. Over the past decade, FTI has been explored in many systems, such as cold atoms[11,12], photonics[13,14], and solid-state systems[1517]. However, directly observing these effects in the above systems is difficult. Consequently, the lack of equivalent visualized systems has greatly hindered further developments of Floquet band engineering.