Yu Shilin, Wang Yusen, Gao Ziang, Li Hao, Song Shaozhe, Yu Jianguo, Zhao Tonggang
Opt Express. 2022 Jan 31;30(3):4084-4095. doi: 10.1364/OE.448933.
Ultra-high quality (Q) factor resonances derived from the bound states in the continuum (BICs) have drawn much attention in optics and photonics. Especially in meta-surfaces, they can enable ultrasensitive sensors, spectral filtering, and lasers because of their enhanced light-matter interactions and rare superiority of scalability. In this paper, we propose a permittivity-asymmetric all-dielectric meta-surface, comprising high-index cuboid tetramer clusters with symmetric structural parameters and configuring periodically on a glass substrate. Simulation results offer dual-band quasi-BICs with high Q values of 4447 and 11391, respectively. Multipolar decomposition in cartesian and electromagnetic distributions are engaged to analyze the physical mechanism of dual quasi-BIC modes, which reveals that they are both governed by magnetic quadrupole (MQ) and in-plane toroidal dipole (TD). The polarization-insensitive and scalable characteristics are also investigated. Additionally, we appraise the sensing performances of the proposed structure. As an example, our work supports an uncommon route to design dual-band polarization-insensitive TD quasi-BICs resonators and facilitates their applications in optic and photonics, such as low-threshold lasers and sensing.
源自连续域束缚态（BICs）的超高品质（Q）因子共振在光学和光子学领域引起了广泛关注。特别是在超表面中，由于其增强的光与物质相互作用以及罕见的可扩展性优势，它们能够实现超灵敏传感器、光谱滤波和激光器。在本文中，我们提出了一种介电常数不对称的全介质超表面，它由具有对称结构参数的高折射率长方体四聚体簇组成，并周期性地配置在玻璃基板上。仿真结果分别提供了具有4447和11391的高Q值的双波段准BICs。采用笛卡尔坐标系中的多极分解和电磁分布来分析双准BIC模式的物理机制，结果表明它们均由磁四极子（MQ）和面内环形偶极子（TD）主导。还研究了其偏振不敏感和可扩展特性。此外，我们评估了所提出结构的传感性能。例如，我们的工作为设计双波段偏振不敏感的TD准BICs谐振器提供了一条不同寻常的途径，并促进了它们在光学和光子学中的应用，如低阈值激光器和传感。
