Bound states in the continuum and exceptional points in dielectric waveguide equipped with a metal grating
Bound states in the continuum and exceptional points in dielectric waveguide equipped with a metal grating
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DOI：
10.1088/1367-2630/ab97e9
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发表时间：
2020-01
影响因子：
3.3
通讯作者：
Ryo Kikkawa;M. Nishida;Y. Kadoya
中科院分区：
文献类型：
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作者：
Ryo Kikkawa;M. Nishida;Y. Kadoya
连续体中的束缚态(BICs)和例外点(EPs)是最近深入研究的主题，因为它们展示了对基础物理和实际应用都具有重要意义的奇异现象。我们研究了Friedrich-Wintgen(FW)型BIC和EP在由金属栅组成的介质波导中的出现，重点讨论了它们对栅厚的依赖关系。对于任意厚度的光栅，BIC出现在由两个波导模形成的反交叉附近的分支上。随着栅厚的变化，抗交叉间隙发生变化，出现BIC的分支发生翻转。结果表明，当缝隙为单模时，BIC出现在空格子(零缝宽)极限的两个波导模的交叉点附近，而结果满足前人关于BIC出现分支的判据。此外，我们还发现，只有在选择栅厚的情况下，EP才会出现在同一器件的BIC附近。包括金属光栅的介质波导中的BIC和EP，特别是具有这种可调谐特性的BIC和EP，除了成为非厄米系统基础研究的平台外，有望导致功能和高性能光子器件的发展。
Bound states in the continuum (BICs) and exceptional points (EPs) have been the subjects of recent intensive research as they exhibit exotic phenomena that are significant for both fundamental physics and practical applications. We investigated the emergence of the Friedrich–Wintgen (FW) type BIC and the EP in a dielectric waveguide comprising a metal grating, focusing on their dependence on the grating thickness. The BIC emerges at a branch near the anti-crossing formed of the two waveguide modes, for a grating of any thickness. With the grating-thickness change, the anti-crossing gap varies and the branch at which the BIC appears flips. We show that, when the slit is single mode, the BIC appears in the vicinity of the crossing between the two waveguide modes in the empty-lattice (zero slit-width) limit, while the results satisfy the criteria for the branch at which the BIC appears in the previous reports. In addition, we find that the EP appears near the BIC in the same device only on selecting the grating thickness. The BIC and EP in the dielectric waveguide comprising a metal grating, particularly with such tunability, are expected to result in the development of functional and high-performance photonic devices in addition to being a platform for the fundamental research of non-Hermitian systems.