Bound States in the Continuum in Asymmetric Dielectric Metasurfaces,Laser & Photonics Reviews

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Bound States in the Continuum in Asymmetric Dielectric Metasurfaces
Laser & Photonics Reviews ( IF 9.8 ) Pub Date : 2022-12-27 , DOI: 10.1002/lpor.202200564
Chaobiao Zhou ₁ , Lujun Huang ₂ , Rong Jin _{3,

4,

5} , Lei Xu ₆ , Guanhai Li _{3,

4,

5} , Mohsen Rahmani ₆ , Xiaoshuang Chen _{3,

4,

5} , Wei Lu _{3,

4,

5} , Andrey E. Miroshnichenko ₂

Affiliation

It is well established that for symmetry-protected bound states in the continuum (BICs), introducing the broken geometry symmetry in a dielectric metasurface transforms such a BIC into a quasi-BIC (QBIC) with high-quality factor (Q-factor). Typically, the smaller the asymmetry parameter, the larger the Q-factor. However, it is very challenging to fabricate such nanostructures with an ultra-small asymmetry parameter, thus limiting the measured Q-factor of QBIC. In this work, the authors demonstrated that BICs can be sustained at Γ-point in an asymmetric dielectric metasurface, whose unit cell is composed of a dielectric cuboid with an off-centre hole inside it. Multipole decompositions and near-field distributions indicate that the toroidal dipole dominates the nature of such a QBIC. Furthermore, the authors found that such a BIC is robust against the shape of the hole. Besides, two BICs at different wavelengths can be achieved by applying either a rectangular hole or a rectangular lattice. Finally, the authors presented experimental verifications of BIC types by fabricating asymmetric silicon metasurfaces. Measurement results show that the Q-factor of QBIC can reach almost 5,000. The results may enrich the library of BICs and find exciting applications in developing high-performance photonics devices, such as nanolasers, biosensors and enhanced nonlinear harmonic generation.

中文翻译：

不对称介电超表面连续体中的束缚态

众所周知，对于连续体 (BIC) 中受对称保护的束缚态，在电介质超曲面中引入几何对称性破缺可将此类 BIC 转换为具有高质量因子（Q 因子）的准 BIC (QBIC)。通常，不对称参数越小，Q 因子越大。然而，制造这种具有超小不对称参数的纳米结构非常具有挑战性，从而限制了 QBIC 的测量 Q 因子。在这项工作中，作者证明了 BIC 可以在不对称电介质超表面的 Γ 点维持，其单位单元由内部有一个偏心孔的电介质长方体组成。多极分解和近场分布表明环形偶极子主导了此类 QBIC 的性质。此外，作者发现这样的 BIC 对孔的形状具有鲁棒性。此外，可以通过应用矩形孔或矩形格子来实现不同波长的两个 BIC。最后，作者通过制造非对称硅超表面展示了 BIC 类型的实验验证。测量结果表明，QBIC 的 Q 因子几乎可以达到 5,000。结果可能会丰富 BIC 库，并在开发高性能光子学设备（例如纳米激光器、生物传感器和增强的非线性谐波生成）方面找到令人兴奋的应用。测量结果表明，QBIC 的 Q 因子几乎可以达到 5,000。结果可能会丰富 BIC 库，并在开发高性能光子学设备（例如纳米激光器、生物传感器和增强的非线性谐波生成）方面找到令人兴奋的应用。测量结果表明，QBIC 的 Q 因子几乎可以达到 5,000。结果可能会丰富 BIC 库，并在开发高性能光子学设备（例如纳米激光器、生物传感器和增强的非线性谐波生成）方面找到令人兴奋的应用。

更新日期：2022-12-27

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