Eyvazi Sioneh, Mamonov Evgeny A, Heilmann Rebecca, Cuerda Javier, Törmä Päivi
Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, Aalto FI-00076, Finland.
ACS Photonics. 2025 Mar 7;12(3):1570-1578. doi: 10.1021/acsphotonics.4c02332. eCollection 2025 Mar 19.
Photonic flat bands are crucial for enabling strong localization of light and enhancing light-matter interactions, as well as tailoring the angular distribution of emission from photonic structures. These unique properties open pathways for developing robust photonic devices, efficient nonlinear optical processes, and novel platforms for exploring topological and quantum phenomena. So far, experimental realizations of lasing in photonic flat bands have been limited to structures that emulate geometrically frustrated lattices in the tight-binding, i.e., short-range coupling, regime. Here, we consider a periodic metasurface with long-range couplings combined with guided modes and report experimental observation of lasing in photonic nearly flat modes. By carefully tuning the thickness of the guiding layer and periodicities, the observed flat lasing spectrum extends up to approximately = 2 μm in reciprocal space. Simulations show that the observed modes exhibit localization in both the waveguiding and active layers. In addition, we observe accidental bound states in the continuum (BICs) at the lasing frequencies, manifesting through polarization vortices with a topological charge || = 1.
光子平带对于实现光的强局域化、增强光与物质的相互作用以及调整光子结构发射的角分布至关重要。这些独特性质为开发稳健的光子器件、高效的非线性光学过程以及探索拓扑和量子现象的新型平台开辟了途径。到目前为止，光子平带中的激光实验实现仅限于在紧束缚（即短程耦合） regime中模拟几何受挫晶格的结构。在这里，我们考虑一种具有长程耦合并结合导模的周期性超表面，并报告在光子近平模中激光的实验观测结果。通过仔细调整引导层的厚度和周期，在倒易空间中观察到的平激光光谱延伸至约 = 2μm。模拟表明，观察到的模式在波导层和有源层中都表现出局域化。此外，我们在激光频率处观察到连续统中的意外束缚态（BICs），通过拓扑电荷 || = 1 的极化涡旋表现出来。
