C points, circular polarization in momentum space, play crucial roles in chiral wave manipulations. However, conventional approaches of achieving intrinsic C points using photonic crystals with broken symmetries suffer from a low Q factor and high sensitivity to structural geometry, rendering them fragile and susceptible to perturbations and disorders. We report magneto-optical (MO) bound states in the continuum (BICs) with a symmetry-preserved planar photonic crystal. We achieve intrinsic C points at Γ point that are robust against variation in both structural geometry and external magnetic field. MO coupling between two modes induces Zeeman splitting, leading to MO BICs and quasi-BICs with circular eigenstates for high- Q chiral responses. Furthermore, switchable C point handedness and circular dichroism are enabled by reversing the magnetic field. These findings unveil BICs and quasi-BICs with circular eigenstates and on-demand control of C points, paving the way for advanced chiral wave manipulation with enhanced light-matter interaction.

中文翻译：

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在连续谱中稳健地生成具有磁光束缚态的本征 C 点


C 点，动量空间中的圆极化，在手性波操纵中起着至关重要的作用。然而，使用具有破坏性对称性的光子晶体实现本征 C 点的传统方法具有低 Q 因子和对结构几何高度敏感的问题，使它们很脆弱，容易受到扰动和无序的影响。我们报道了连续体 （BIC） 中的磁光 （MO） 束缚态，具有对称性保持的平面光子晶体。我们在 Γ 点上实现了固有的 C 点，这些点对结构几何形状和外部磁场的变化都具有鲁棒性。两种模式之间的 MO 偶联诱导塞曼分裂，导致 MO BICs 和准 BICs 具有圆形特征态，以实现高 Q 手性响应。此外，通过反转磁场，可实现可切换的 C 点旋性和圆二色性。这些发现揭示了具有圆形特征态和按需控制 C 点的 BICs 和准 BIC，为具有增强光-物质相互作用的高级手性波操纵铺平了道路。