Liu Weijie, Liu Quancheng, Ni Xiang, Jia Yuechen, Ziegler Klaus, Alù Andrea, Chen Feng
School of Physics, State Key Laboratory of Crystal Materials, Shandong University, 250100, Jinan, China.
Department of Physics, Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan, 52900, Israel.
Nat Commun. 2024 Jan 31;15(1):946. doi: 10.1038/s41467-024-45226-x.
Parity-time (PT) symmetry has been unveiling new photonic regimes in non-Hermitian systems, with opportunities for lasing, sensing and enhanced light-matter interactions. The most exotic responses emerge at the exceptional point (EP) and in the broken PT-symmetry phase, yet in conventional PT-symmetric systems these regimes require large levels of gain and loss, posing remarkable challenges in practical settings. Floquet PT-symmetry, which may be realized by periodically flipping the effective gain/loss distribution in time, can relax these requirements and tailor the EP and PT-symmetry phases through the modulation period. Here, we explore Floquet PT-symmetry in an integrated photonic waveguide platform, in which the role of time is replaced by the propagation direction. We experimentally demonstrate spontaneous PT-symmetry breaking at small gain/loss levels and efficient control of amplification and suppression through the excitation ports. Our work introduces the advantages of Floquet PT-symmetry in a practical integrated photonic setting, enabling a powerful platform to observe PT-symmetric phenomena and leverage their extreme features, with applications in nanophotonics, coherent control of nanoscale light amplification and routing.
宇称时间（PT）对称性一直在非厄米系统中揭示新的光子学机制，为激光发射、传感及增强光与物质的相互作用带来了机遇。最奇特的响应出现在例外点（EP）和PT对称破缺相中，然而在传统的PT对称系统中，这些机制需要大量的增益和损耗，这在实际应用中带来了巨大挑战。弗洛凯PT对称性可以通过周期性地及时翻转有效增益/损耗分布来实现，它可以放宽这些要求，并通过调制周期来调整例外点和PT对称相。在此，我们在集成光子波导平台中探索弗洛凯PT对称性，其中时间的作用被传播方向所取代。我们通过实验证明了在小增益/损耗水平下的自发PT对称破缺，以及通过激发端口对放大和抑制的有效控制。我们的工作介绍了弗洛凯PT对称性在实际集成光子学环境中的优势，为观察PT对称现象并利用其极端特性提供了一个强大的平台，可应用于纳米光子学、纳米级光放大和路由的相干控制。
