近日，武汉纺织大学的汪胜祥&朱伟及其研究团队取得一项新进展。经过不懈努力，他们基于混合一维光子晶体异质结构中耦合界面态的PT相变实现角度不敏感传输与吸收。相关研究成果已于2024年5月3日在国际知名学术期刊《物理评论A》上发表。

在这项工作中，研究人员开发了一种由两种拓扑结构不同的异质结构组成的杂化光子晶体，这两种异质结构都具备角度不敏感的带隙特性。该杂化光子晶体能够维持两种拓扑界面态（TISs），从而被视为一个光学非厄米系统。通过精细调控这些TISs之间的耦合作用，研究人员成功实现了完美的波传输，并揭示了宇称时间（PT）相变，这一点通过透射光谱的演变得到了验证。值得一提的是，由于异质结构的宽角度光子带隙特性，波的完美传输对入射角度的波动具有高度的鲁棒性。

此外，他们还探索了另一种杂化光子晶体异质结构，该结构拥有两个界面通道，分别支持TIS和塔姆等离子体极化子。当这两种模式之间的耦合增强时，观察到了两个明显的共振峰。通过逐渐减弱这种耦合，这些峰最终合并为一个单一的峰。在PT相变的情况下，实现了完美的波吸收。令人瞩目的是，透射和吸收峰的频移在0°到90°的角度变化范围内保持极小（Δf=1.4THz），显示出显著的稳定性。这些结果进一步扩展和补充了正在进行的非厄米拓扑物理的探索。

据悉，非厄米系统提供了操纵电磁波的新方法，包括在传感和模式转换中的应用，吸引了极大的研究兴趣。

附：英文原文

Title: Angle-insensitive transmission and absorption with a PT phase transition via coupled interface states in hybrid one-dimensional photonic crystal heterostructures

Author: Guochao Wei, Beibei Wang, Kang Du, Bohan Zhang, Cai Zhou, Tingting Wang, Weijia Han, Wei Zhu, Shengxiang Wang

Issue&Volume: 2024/05/03

Abstract: Non-Hermitian systems offer novel methods for manipulating electromagnetic waves, including applications in sensing and mode conversion, attracting significant research interest. In this work, we propose a hybrid photonic crystal comprised of two topologically distinct heterostructures with angle-insensitive band gaps. This hybrid photonic crystal can sustain two topological interface states (TISs), and is considered as an optical non-Hermitian system. By precisely tuning of the coupling between these TISs, we achieve perfect wave transmission, revealing a parity-time (PT) phase transition, as evidenced by the evolution of the transmission spectra. Remarkably, the perfect transmission of waves remains resilient against fluctuating incident angles, ensured by the angle-tolerant photonic band gaps of the heterostructures. Additionally, we explore another hybrid photonic crystal heterostructure featuring two interface channels supporting the TIS and the Tamm plasma polariton. As the coupling between these two modes strengthens, two distinct resonance peaks emerge. Gradually reducing this coupling results in the merging of these peaks into a single peak. As the PT phase transition case, perfect wave absorption can be realized. Notably, the frequency shifts of the transmission and absorption peaks remain minimal, demonstrating a remarkable stability with an angle variation from 0° to 90° (Δf=1.4THz). These results further expand and complement the ongoing exploration of non-Hermitian topological physics.

DOI: 10.1103/PhysRevA.109.053504

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.109.053504