Dong Zhaohui, Chen Xianfeng, Yuan Luqi
State Key Laboratory of Photonics and Communications, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China.
Shandong Normal University, Collaborative Innovation Center of Light Manipulation and Applications, Jinan 250358, China.
Phys Rev Lett. 2025 Jul 18;135(3):033803. doi: 10.1103/4lqd-z567.
The moiré superlattice has attracted growing interest in the electromagnetic and optical communities. Here, we extend this concept to time-varying photonic systems by superposing two binary modulations on the refractive index with different modulation periods, i.e., the moiré photonic time crystal (PTC). Such a moiré PTC leads to extremely narrow bands in momentum space that support temporal localized modes, exhibiting periodically self-reconstructing pulses in the time domain. We investigate the tunability of the band structure of the moiré PTC and the temporal localization behavior, which can be greatly manipulated by varying the temporal modulation parameters. Moreover, we explore the Floquet mode-locking mechanism in the moiré PTC, which points toward potential applications in mode-locked lasers with a tunable time width of the generated pulses. The modulation-induced extremely narrow band also offers intriguing opportunities in exceptional-point-enhanced sensing. Our Letter brings the concept of moiré patterns to the field of PTCs, and unveils new possibilities in wave manipulations with time-varying systems.
莫尔超晶格在电磁和光学领域引起了越来越多的关注。在此，我们通过将具有不同调制周期的两种二元调制叠加在折射率上，将这一概念扩展到时变光子系统，即莫尔光子时间晶体（PTC）。这样的莫尔PTC在动量空间中导致极窄的能带，这些能带支持时间局域模式，在时域中表现出周期性的自重构脉冲。我们研究了莫尔PTC能带结构的可调性和时间局域行为，通过改变时间调制参数可以对其进行极大的操控。此外，我们探索了莫尔PTC中的弗洛凯模式锁定机制，这指向了在具有可调脉冲时间宽度的锁模激光器中的潜在应用。调制引起的极窄能带在异常点增强传感方面也提供了有趣的机会。我们的信函将莫尔图案的概念引入到PTC领域，并揭示了时变系统在波操控方面的新可能性。
