You Shaojun, Zhou Mimi, Xu Lei, Chen Deliang, Fan Menghui, Huang Jing, Ma Wenbin, Luo Shengyun, Rahmani Mohsen, Zhou Chaobiao, Miroshnichenko Andrey E, Huang Lujun
School of Physics and Mechatronic Engineering, Guizhou Minzu University, Guiyang 550025, China.
School of Chemical Engineering, Guizhou Minzu University, Guiyang 550025, China.
Nanophotonics. 2023 May 1;12(11):2051-2060. doi: 10.1515/nanoph-2023-0166. eCollection 2023 May.
Symmetry-protected bound states in the continuum (SP-BICs) are one of the most intensively studied BICs. Typically, SP-BICs must be converted into quasi-BICs (QBICs) by breaking the unit cell's symmetry so that they can be accessed by the external excitation. The symmetry-broken usually results in a varied resonance wavelength of QBICs which are also highly sensitive to the asymmetry parameters. In this work, we demonstrate that QBICs with a stable resonance wavelength can be realized by breaking translational symmetry in an all-dielectric metasurface. The unit cell of metasurface is made of a silicon nanodisk dimer. The Q-factor of QBICs is precisely tuned by changing the interspacing of two nanodisks while their resonance wavelength is quite stable against the interspacing. We also find that such BICs show weak dependence on the shape of the nanodisk. Multiple decompositions indicate that the toroidal dipole dominates this type of QBIC. The resonance wavelengths of QBICs can be tuned only by changing either the lattice constants or the radius of nanodisk. Finally, we present experimental demonstrations on such a QBIC with a stable resonance wavelength. The highest measured Q-factor of QBICs is >3000. Our results may find promising applications in enhancing light-matter interaction.
连续统中的对称性保护束缚态（SP-BICs）是研究最为深入的BICs之一。通常情况下，必须通过破坏晶胞的对称性将SP-BICs转换为准BICs（QBICs），以便它们能够被外部激发所激发。对称性破坏通常会导致QBICs的共振波长发生变化，并且它们对不对称参数也高度敏感。在这项工作中，我们证明了通过破坏全介质超表面中的平移对称性，可以实现具有稳定共振波长的QBICs。超表面的晶胞由硅纳米盘二聚体构成。通过改变两个纳米盘之间的间距，可以精确调节QBICs的品质因数，而它们的共振波长对间距相当稳定。我们还发现，这种BICs对纳米盘的形状依赖性较弱。多重分解表明，环形偶极子主导了这种类型的QBIC。QBICs的共振波长只能通过改变晶格常数或纳米盘的半径来调节。最后，我们展示了关于这种具有稳定共振波长的QBIC的实验演示。测量到的QBICs的最高品质因数大于3000。我们的结果可能在增强光与物质相互作用方面找到有前景的应用。
