Merging toroidal dipole bound states in the continuum without up-down symmetry in Lieb lattice metasurfaces
Merging toroidal dipole bound states in the continuum without up-down symmetry in Lieb lattice metasurfaces
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DOI：
10.1515/nanoph-2023-0686
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发表时间：
2023-07
期刊：
影响因子：
7.5
通讯作者：
Guodong Zhu;Sen Yang;Justus C. Ndukaife
中科院分区：
文献类型：
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作者：
Guodong Zhu;Sen Yang;Justus C. Ndukaife
摘要连续统(BICs)中束缚态的意义在于它们在理论上具有无限质量因子的势。然而，它们的实际品质因数受到制造缺陷的限制，这导致了与辐射连续谱的耦合。在这项研究中，我们提出了一种新的方法来解决这个问题，引入了一种基于Lieb格的合并BIC机制。通过这种方法，我们有效地抑制了面外散射损耗，从而增强了结构对制造伪影的稳健性。值得注意的是，与以前的合并系统不同，我们的设计不依赖于超曲面的上下对称。这一特性在涉及具有不同光学性质的衬底和上层的应用中提供了更大的灵活性，例如微流控器件。此外，我们在设计中加入了横向带隙反射镜来封装BIC结构。这种反射镜可以抑制有限尺寸效应引起的面内辐射，使品质因数显著提高十倍。因此，由LIEB晶格光子晶体反射镜包围的合并的BIC金属表面，在保持26.6x26.6μm的小占地面积的同时，达到了非常高的质量系数105.我们的发现建立了一个吸引人的平台，利用了紧凑结构中BIC的拓扑性质。该平台具有广泛的应用前景，包括光学捕获、光流体和高灵敏度生物检测，为这些领域开辟了新的可能性。
Abstract The significance of bound states in the continuum (BICs) lies in their potential for theoretically infinite quality factors. However, their actual quality factors are limited by imperfections in fabrication, which lead to coupling with the radiation continuum. In this study, we present a novel approach to address this issue by introducing a merging BIC regime based on a Lieb lattice. By utilizing this approach, we effectively suppress the out-of-plane scattering loss, thereby enhancing the robustness of the structure against fabrication artifacts. Notably, unlike previous merging systems, our design does not rely on the up-down symmetry of metasurfaces. This characteristic grants more flexibility in applications that involve substrates and superstrates with different optical properties, such as microfluidic devices. Furthermore, we incorporate a lateral band gap mirror into the design to encapsulate the BIC structure. This mirror serves to suppress the in-plane radiation resulting from finite-size effects, leading to a remarkable ten-fold improvement in the quality factor. Consequently, our merged BIC metasurface, enclosed by the Lieb lattice photonic crystal mirror, achieves an exceptionally high-quality factor of 105 while maintaining a small footprint of 26.6 × 26.6 μm. Our findings establish an appealing platform that capitalizes on the topological nature of BICs within compact structures. This platform holds great promise for various applications, including optical trapping, optofluidics, and high-sensitivity biodetection, opening up new possibilities in these fields.