Zhang Haosen, Wu Kedi, Wang Guo Ping
Opt Lett. 2024 Apr 1;49(7):1692-1695. doi: 10.1364/OL.517673.
All-dielectric high-Q metasurface absorbers based on quasi-bound states in the continuum (QBICs) are essential for optical and photonic devices. However, achieving perfect absorption requires adding back reflectors at the bottom or placing at least four asymmetric elements in each unit of monolayer metasurfaces, which will increase the design complexity. This work proposes a honeycomb structure with units periodically arranged as a hexagonal lattice. Each unit cell is made of two nanopost elements. By only tuning the radius difference of two elements to break the in-plane symmetry, two orthogonal QBIC modes corresponding to toroidal dipole (TD) and electric dipole (ED) modes are excited, respectively. The maximum absorption reaches 92.3% at 955 nm with a Q factor of 1501, breaking the monolayer limit of 50% by the degenerate critical coupling. Our work may provide a promising route for designing high-Q all-dielectric metasurface absorbers applied in ultrafast optoelectronic devices.
基于连续体中的准束缚态（QBICs）的全介质高Q值超表面吸收器对于光学和光子器件至关重要。然而，要实现完美吸收需要在底部添加背反射器，或者在单层超表面的每个单元中放置至少四个不对称元件，这会增加设计复杂性。这项工作提出了一种蜂窝结构，其单元以六边形晶格周期性排列。每个单元由两个纳米柱元件组成。通过仅调整两个元件的半径差来打破面内对称性，分别激发了对应于环形偶极子（TD）和电偶极子（ED）模式的两个正交QBIC模式。在955 nm处最大吸收率达到92.3%，品质因数为1501，通过简并临界耦合打破了50%的单层极限。我们的工作可能为设计应用于超快光电器件的高Q值全介质超表面吸收器提供一条有前景的途径。
