Ren Boquan, Arkhipova Antonina A, Zhang Yiqi, Kartashov Yaroslav V, Wang Hongguang, Zhuravitskii Sergei A, Skryabin Nikolay N, Dyakonov Ivan V, Kalinkin Alexander A, Kulik Sergei P, Kompanets Victor O, Chekalin Sergey V, Zadkov Victor N
Key Laboratory for Physical Electronics and Devices, Ministry of Education, School of Electronic Science and Engineering, Xi'an Jiaotong University, Xi'an, 710049, China.
Institute of Spectroscopy, Russian Academy of Sciences, Troitsk, Moscow, 108840, Russia.
Light Sci Appl. 2023 Aug 10;12(1):194. doi: 10.1038/s41377-023-01235-x.
Introduction of controllable deformations into periodic materials that lead to disclinations in their structure opens novel routes for construction of higher-order topological insulators hosting topological states at disclinations. Appearance of these topological states is consistent with the bulk-disclination correspondence principle, and is due to the filling anomaly that results in fractional charges to the boundary unit cells. So far, topological disclination states were observed only in the linear regime, while the interplay between nonlinearity and topology in the systems with disclinations has been never studied experimentally. We report here on the experimental observation of the nonlinear photonic disclination states in waveguide arrays with pentagonal or heptagonal disclination cores inscribed in transparent optical medium using the fs-laser writing technique. The transition between nontopological and topological phases in such structures is controlled by the Kekulé distortion coefficient r with topological phase hosting simultaneously disclination states at the inner disclination core and spatially separated from them corner-I, corner-II, and extended edge states at the outer edge of the structure. We show that the robust nonlinear disclination states bifurcate from their linear counterparts and that location of their propagation constants in the gap and, hence, their spatial localization can be controlled by their power. Nonlinear disclination states can be efficiently excited by Gaussian input beams, but only if they are focused into the waveguides belonging to the disclination core, where such topological states reside. Our results open new prospects for investigation of nonlinear effects in topological systems with disclinations and are relevant for different areas of science, including Bose-Einstein and polariton condensates, where potentials with the disclinations can be created.
在周期性材料中引入可控变形，使其结构中产生位错，为构建高阶拓扑绝缘体开辟了新途径，这种高阶拓扑绝缘体在位错处存在拓扑态。这些拓扑态的出现符合体-位错对应原理，是由于填充反常导致边界晶胞出现分数电荷。到目前为止，拓扑位错态仅在线性 regime 中被观测到，而在位错系统中非线性与拓扑之间的相互作用从未有过实验研究。我们在此报告利用飞秒激光写入技术在透明光学介质中刻有五边形或七边形位错核的波导阵列中对非线性光子位错态的实验观测。这种结构中非拓扑相和拓扑相之间的转变由凯库勒畸变系数 r 控制，拓扑相中在位错核心内部同时存在位错态，并且在结构外边缘与它们在空间上分离的角 I、角 II 和扩展边缘态。我们表明，稳健的非线性位错态从其线性对应态分叉出来，并且它们在能隙中的传播常数位置以及因此它们的空间局域化可以由其功率控制。非线性位错态可以被高斯输入光束有效激发，但前提是它们被聚焦到属于位错核心的波导中，这种拓扑态就存在于这些波导中。我们的结果为研究具有位错的拓扑系统中的非线性效应开辟了新前景，并且与包括玻色-爱因斯坦凝聚体和极化激元凝聚体在内的不同科学领域相关，在这些领域中可以创建具有位错的势场。
