Tunable Localization of Higher-Order Bound States in Non-Hermitian Optical Waveguide Lattices,Laser & Photonics Reviews

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Tunable Localization of Higher-Order Bound States in Non-Hermitian Optical Waveguide Lattices
Laser & Photonics Reviews ( IF 9.8 ) Pub Date : 2023-10-04 , DOI: 10.1002/lpor.202300558
Juan Kang _{1,

2} , Qinglong Zhang ₁ , Ruishan Wei ₁ , Jianrong Qiu ₃ , Zhongmin Yang ₄ , Guoping Dong ₁

Affiliation

Higher-order corner-bound states in a 2D structure have been found to possess robust and exotic properties beyond the “ordinary” topological edge states, giving rise to a promising applicative potential. For example, the topological nanocavity designed based on the corner states exhibits much better performance than that of the conventional photonic crystal cavity. However, the corner states in the finite Hermitian system are usually coupled with each other, which results in the weakening of their localization. As such, the contradiction between the performance and footprint of topological devices is vexing. Here, it shows that introducing non-Hermiticity in the higher-order topological insulators is an effective strategy to enhance the localization of corner states in finite systems. By designing and analyzing the 2D finite Su-Schriffer-Heeger optical lattices with two types of non-Hermitian configuration, the localization degree of higher-order corner states is found to depend on the gain/loss strength. This is experimentally demonstrated by observing the distribution of corner states in the femtosecond-laser-writing loss-controlled waveguide arrays. This scheme tuning localization of higher-order corner-bound states by non-Hermiticity may offer a new avenue to design robust and compact devices, such as topological nano-lasers with an ultra-low threshold.

中文翻译：

非厄米光波导晶格中高阶束缚态的可调谐局域化

人们发现，二维结构中的高阶角束缚态具有超越“普通”拓扑边缘态的鲁棒性和奇特特性，从而产生了广阔的应用潜力。例如，基于角态设计的拓扑纳米腔表现出比传统光子晶体腔更好的性能。然而，有限埃尔米特系统中的角态通常相互耦合，导致其局域化减弱。因此，拓扑器件的性能和占用空间之间的矛盾令人烦恼。在这里，它表明在高阶拓扑绝缘体中引入非厄米性是增强有限系统中角态局域化的有效策略。通过设计和分析两种非厄米结构的二维有限Su-Schriffer-Heeger光学晶格，发现高阶角态的局域化程度取决于增益/损耗强度。通过观察飞秒激光写入损耗控制波导阵列中角态的分布，实验证明了这一点。这种通过非厄米性调节高阶角束缚态局域化的方案可能为设计坚固且紧凑的器件（例如具有超低阈值的拓扑纳米激光器）提供新途径。

更新日期：2023-10-04

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