Topological Band Gaps Enlarged in Epsilon-Near-Zero Magneto-Optical Photonic Crystals
Topological Band Gaps Enlarged in Epsilon-Near-Zero Magneto-Optical Photonic Crystals
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Epsilon 近零磁光光子晶体中拓扑带隙增大
DOI：
10.1021/acsphotonics.1c01942
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发表时间：
2022
期刊：
影响因子：
7
通讯作者：
and Satoshi Iwamoto
中科院分区：
文献类型：
--
作者：
Tianji Liu;Nobukiyo Kobayashi;Kenji Ikeda;Yasutomo Ota;and Satoshi Iwamoto
拓扑光子学为光的操纵提供了令人兴奋和新兴的机会。作为量子霍尔边缘态的光子模拟，手性边缘模式产生于两个不同陈恩数的光子拓扑结构之间的界面上，在克服障碍和缺陷的强健光输运方面具有很大的前景。然而，对于基于磁光材料的拓扑光子晶体，手性边缘模式的输运性能强烈依赖于拓扑间隙尺寸，由于缺乏具有强非互反响应的磁光材料，在光学频率下，拓扑间隙通常非常窄。在这里，我们用数值证明了在磁光光子晶体中引入epsilon-near-zero效应可以显著地扩大拓扑间隙尺寸，这是由于磁光响应的增强。本征模计算结果表明，磁光响应的增强与具有接近零对角介电常数的磁化光子晶体的非互易功率流的增强有关。扩大的拓扑带隙导致沿两个相反磁化光子晶体之间的磁化边界传播的宽带和良好约束的手性边缘模式。更重要的是，这种模式传播对急弯和大缺陷具有很强的鲁棒性。原则上，我们关于拓扑光子带隙扩大的建议也适用于光子晶体板甚至三维光子晶体。我们的研究结果不仅表明了提高磁光光子晶体中单向模式输运性能的可能性，而且丰富了对基于epsilon近零效应的拓扑光子学的物理理解。
Topological photonics provides exciting and emerging opportunities for the manipulation of light. As the photonic analogue of quantum Hall edge states, chiral edge modes, arising at the interface between two photonic topological structures with different Chern numbers, hold great promise for robust transport of light against disorders and defects. However, for magneto-optical material-based topological photonic crystals, the transport performance of chiral edge modes is strongly dependent on the topological gap sizes, which are usually very narrow at optical frequencies due to the lack of magneto-optical materials with strong nonreciprocal responses. Here, we numerically demonstrated that the introduction of an epsilon-near-zero effect to magneto-optical photonic crystals could remarkably enlarge topological gap sizes due to the boosted magneto-optical response. Eigenmode calculation results show that the boosted magneto-optical response correlates to the enhanced nonreciprocal power flows in magnetized photonic crystals with an epsilon-near-zero diagonal permittivity. The enlarged topological band gap leads to the broadband and well-confined chiral edge modes propagating along the magnetized boundary between two oppositely magnetized photonic crystals. More importantly, such mode propagation shows strong robustness against sharp bends and large defects. In principle, our proposal for the enlargement of topological photonic band gaps could also be valid in photonic crystal slabs or even three-dimensional photonic crystals. Our results not only suggest the possibility to improve the transport performance of one-way modes in magneto-optical photonic crystals but also enrich the physical understanding of the epsilon-near-zero effect-based topological photonics.