Qin Haoyu, Chen Shaohu, Zhang Weixuan, Zhang Huizhen, Pan Ruhao, Li Junjie, Shi Lei, Zi Jian, Zhang Xiangdong
Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurements of Ministry of Education, School of Physics, Beijing Institute of Technology, 100081, Beijing, China.
Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems, School of Physics, Beijing Institute of Technology, 100081, Beijing, China.
Nat Commun. 2024 Oct 21;15(1):9080. doi: 10.1038/s41467-024-53433-9.
Trapping electromagnetic waves within the radiation continuum holds significant implications in the field of optical science and technology. Photonic bound states in the continuum (BICs) present a distinctive approach for achieving this functionality, offering potential applications in laser systems, sensing technologies, and other domains. However, the simultaneous achievement of high Q-factors, flat-band dispersions, and wide-angle responses in photonic BICs has not yet been reported, thereby impeding their practical performance due to laser direction deviation or sample disorder. Here, we theoretically demonstrate the construction of moiré BICs in one-dimensional photonic crystal (PhC) slabs, where high-Q resonances in the entire moiré flat band are achieved. Specifically, we numerically validate that the radiation loss of moiré BICs can be eliminated by aligning multiple topological polarization charges with all diffraction channels, enabling the strong suppression of far-field radiation from the entire moiré band. This leads to a slow decay of Q-factors away from moiré BICs in the momentum space. Moreover, it is found that Q-factors of the moiré flat band can still maintain at a high level with structural disorder. In experiments, we fabricate the designed 1D moiré PhC slab and observe both high-Q resonances and a slow decrease of Q-factors for moiré flat-band Bloch modes. Our findings hold promising implications for designing highly efficient optical devices with wide-angle responses and introduce a novel avenue for exploring BICs in moiré superlattices.
将电磁波捕获在辐射连续谱内对光学科学与技术领域具有重大意义。连续谱中的光子束缚态（BICs）为实现这一功能提供了一种独特方法，在激光系统、传感技术及其他领域具有潜在应用价值。然而，光子BICs同时实现高Q因子、平带色散和广角响应的情况尚未见报道，这因激光方向偏差或样品无序而阻碍了其实际性能。在此，我们从理论上证明了在一维光子晶体（PhC）平板中构建莫尔BICs，其中在整个莫尔平带中实现了高Q共振。具体而言，我们通过数值验证，通过使多个拓扑极化电荷与所有衍射通道对齐，可以消除莫尔BICs的辐射损耗，从而能够强烈抑制整个莫尔带的远场辐射。这导致在动量空间中远离莫尔BICs时Q因子缓慢衰减。此外，发现莫尔平带的Q因子在结构无序情况下仍能保持在较高水平。在实验中，我们制备了设计的一维莫尔PhC平板，并观察到莫尔平带布洛赫模式的高Q共振和Q因子的缓慢下降。我们的研究结果对于设计具有广角响应的高效光学器件具有广阔前景，并为探索莫尔超晶格中的BICs引入了一条新途径。
