Lu Qijing, Feng Ziyao, Sun Xiankai
Department of Electronic Engineering, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China.
Key Laboratory of Optoelectronic Science and Technology for Medicine of Ministry of Education, Provincial Key Laboratory for Photonics Technology, Fujian Normal University, Fuzhou 350007, China.
Nanophotonics. 2024 Aug 2;13(18):3527-3534. doi: 10.1515/nanoph-2024-0196. eCollection 2024 Aug.
Bound states in the continuum (BICs) have attracted much attention in the field of nanophotonics owing to their ability to trap photons without loss. Recently, a low-refractive-index (RI) waveguide loaded on a high-RI slab structure was demonstrated to support BICs. However, strict control of structural parameters is required due to the accidental nature of those BICs. Here, we propose a novel structure consisting of two low-RI vertically coupled waveguides loaded on a high-RI slab. This structure supports symmetry-protected BICs (SP-BICs), which do not require strict control of the geometric parameters. Such SP-BICs can also possess an infinitely high quality factor in resonant structures, which can be harnessed for ultranarrow-bandwidth spatial and spectral filters. Our work opens a new way of harnessing BICs on an integrated photonic platform for realizing nanophotonic circuits and devices.
连续域束缚态（BICs）因其能够无损耗地捕获光子而在纳米光子学领域备受关注。最近，有人证明在高折射率平板结构上加载低折射率（RI）波导能够支持BICs。然而，由于这些BICs的偶然性，需要严格控制结构参数。在此，我们提出一种新型结构，它由加载在高折射率平板上的两个垂直耦合的低折射率波导组成。这种结构支持对称性保护的BICs（SP-BICs），其不需要严格控制几何参数。这种SP-BICs在谐振结构中也可以具有无限高的品质因数，可用于超窄带宽空间和光谱滤波器。我们的工作为在集成光子平台上利用BICs实现纳米光子电路和器件开辟了一条新途径。
