论文标题
在双层结构上连续体中传播结合状态的有条件鲁棒性
Conditional robustness of propagating bound states in the continuum on biperiodic structures
论文作者
论文摘要
对于夹在两个均匀介质之间的周期性结构，连续体（BIC）中的结合状态是带导的Bloch模式，辐射连续体中的频率为频率。光学BIC发现了许多应用，主要是因为它们引起了超高质量因素的共鸣。如果周期性结构具有相关的对称性，则BIC可能具有对称性不匹配，并具有相同频率和兼容波形的传入和外向的传播波，并且被认为是由对称性保护的。在许多高度对称的周期性结构上发现了具有非零BLOCH波矢的传播BIC。它们不受通常意义上的对称的保护（即没有对称性不匹配），但是其中一些似乎取决于对称性的存在和鲁棒性。在本文中，我们表明，在周期性平面上具有反转对称性的双层结构上的低频传播BIC（仅一个辐射通道），并且在垂直方向上具有反射对称性，可以强大地对对称性的结构性构成。换句话说，当双层结构略微保存倒置和反射对称性时，传播BIC以略有不同的频率和略有不同的bloch波形继续存在。我们的研究增强了对周期结构的理论理解，并为其应用提供了有用的指南。
For a periodic structure sandwiched between two homogeneous media, a bound state in the continuum (BIC) is a guided Bloch mode with a frequency in the radiation continuum. Optical BICs have found many applications, mainly because they give rise to resonances with ultra-high quality factors. If the periodic structure has a relevant symmetry, a BIC may have a symmetry mismatch with incoming and outgoing propagating waves of the same frequency and compatible wavevectors, and is considered as protected by symmetry. Propagating BICs with nonzero Bloch wavevectors have been found on many highly symmetric periodic structures. They are not protected by symmetry in the usual sense (i.e., there is no symmetry mismatch), but some of them seem to depend on symmetry for their existence and robustness. In this paper, we show that the low-frequency propagating BICs (with only one radiation channel) on biperiodic structures with an inversion symmetry in the plane of periodicity and a reflection symmetry in the perpendicular direction are robust to symmetry-preserving structural perturbations. In other words, a propagating BIC continues its existence with a slightly different frequency and a slightly different Bloch wavevector, when the biperiodic structure is perturbed slightly preserving the inversion and reflection symmetries. Our study enhances theoretical understanding for BICs on periodic structures and provides useful guidelines for their applications.
