Mao Wenbo, Li Fu, Zhang Qian, Xu Weijie, Awan Kashif Masud, Yang Lan
Department of Electrical and Systems Engineering, Washington University, St Louis, MO 63130, USA.
Institute of Materials Science and Engineering, Washington University, St Louis, MO 63130, USA.
Sci Adv. 2025 Mar 7;11(10):eadu4653. doi: 10.1126/sciadv.adu4653.
Phase transition in parity-time (PT) symmetry is one of the most intriguing discoveries in non-Hermitian physics, giving rise to plenty of physical phenomena and strategies to develop advanced devices and systems, such as unconventional lasers, nonreciprocal transmission, and enhanced sensitivity. Floquet PT-symmetric systems are characterized by time-periodic Hamiltonians, in which the gain or loss is modulated to steer the PT phase, providing an additional dimension for realizing phase transitions. In this study, we introduce frequency-varying modulation, specifically spatially chirped modulation, into on-chip Floquet PT-symmetric photonic waveguides to explore their unique properties. The waveguides exhibit distinct forward and backward transmissions when the system dynamically evolves around phase transition points, i.e., exceptional points. Furthermore, reconfigurable asymmetric transmission systems are developed by integrating tunable mode switches. Combining non-Hermitian physics with the advanced technologies of photonic integrated circuits holds great potential to create devices and systems with improved functionalities and enhanced performance.
宇称时间（PT）对称中的相变是非厄米物理学中最引人入胜的发现之一，它引发了大量物理现象以及开发先进器件和系统的策略，例如非常规激光器、非互易传输和增强灵敏度。弗洛凯PT对称系统的特点是具有时间周期哈密顿量，其中增益或损耗被调制以控制PT相，为实现相变提供了一个额外维度。在本研究中，我们将频率变化调制，特别是空间啁啾调制，引入到片上弗洛凯PT对称光子波导中，以探索其独特性质。当系统围绕相变点（即例外点）动态演化时，波导表现出明显的正向和反向传输。此外，通过集成可调模式开关开发了可重构非对称传输系统。将非厄米物理学与光子集成电路的先进技术相结合，在创建具有改进功能和增强性能的器件和系统方面具有巨大潜力。
