标题： 增强的$Q$因子和光子连续态在局部弯曲轨迹处合并的鲁棒性 显示英文标题

标题： Enhanced $Q$ factor and robustness of photonic bound states in the continuum merging at locally bent trajectories

摘要： 连续域中的束缚态（BIC）在平面光子结构中引起了广泛的科学兴趣，因为它们具有出色的光 confinement 能力。某些 BIC 的拓扑鲁棒性允许通过调整结构的几何参数来改变它们在动量空间中的位置。在这项工作中，我们研究了一维周期光栅中的一个 BIC，并发现其动量空间位置可以成为某个几何参数的非单调函数，形成局部弯曲的“V”形轨迹。我们表明，在该轨迹的拐点附近，BIC 的鲁棒性和其 $Q$ 因子可以大大增强。我们将这种“V-BIC”调节到几乎与对称保护的 BIC 在 $\Gamma$-点处合并。这形成了一个包含 BIC 的“K”形超高 $Q$ 区域，与普通合并的 BIC 相比，该 BIC 具有更高且更稳定的 $Q$ 因子。还发现，“K-BIC”在有限光栅中提供了在极宽范围几何参数下 $Q$ 因子的强大增强。我们的发现促进了超高 $Q$ BIC 及其应用的发展。 显示英文摘要

摘要： Bound states in the continuum (BICs) in planar photonic structures have attracted broad scientific interest owing to their exceptional capability to confine light. Topological robustness of certain BICs allows them to be moved in the momentum space by tuning the geometric parameters of the structure. In this work, we study such a BIC in a one-dimensional periodic grating, and find that its momentum-space position can be made a non-monotonic function of a geometric parameter, forming a locally bent ''V''-shaped trajectory. We show that, near the turning point of this trajectory, the robustness of the BIC and its $Q$ factor can be greatly enhanced. We tune such ''V-BICs'' to almost merge with a symmetry-protected BIC at the $\Gamma$-point. This creates a ''K''-shaped ultrahigh-$Q$ region containing a BIC with a much higher and more stable $Q$ factor compared to the ordinary merging BICs. The ''K-BICs'' are also found to provide a strong enhancement of the $Q$ factor in finite gratings over an extremely wide range of geometric parameters. Our findings enable further advancements in the development of ultrahigh-$Q$ BICs and their applications.