Hsiao Hui-Hsin, Hsieh Jou-Chun, Liu Ai-Yin, Lin Kuang-I, Hsu Yi-Chien
Department of Engineering Science and Ocean Engineering, National Taiwan University, Taipei 10617, Taiwan.
Institute of Electro-Optical Engineering, National Taiwan Normal University, Taipei 11677, Taiwan.
Nanophotonics. 2024 Jun 3;13(17):3155-3164. doi: 10.1515/nanoph-2024-0194. eCollection 2024 Jul.
We develop a new all-dielectric metasurface for designing high quality-factor (-factor) quasi-bound states in the continuum (quasi-BICs) using asymmetry kite-shaped nanopillar arrays. The -factors of quasi-BICs follow the quadratic dependence on the geometry asymmetry, and meanwhile their resonant spectral profiles can be readily tuned between Fano and Lorentzian lineshapes through the interplay with the broadband magnetic dipole mode. The third-harmonic signals of quasi-BIC modes exhibit a gain from 43.4- to 634-fold enhancement between samples with an axial-length difference of 15 nm and 75 nm when reducing the numerical aperture of the illuminating objective lenses in nonlinear measurement, which is attributed to the increasing illumination spot size and the less contribution from the large oblique incident light for establishing quasi-BIC modes with high- spectral profile and strong near-field intensity. The silicon-based metasurfaces with their simple geometry are facile for large-area fabrication and open new possibilities for the optimization of upconversion processes to achieve efficient nonlinear devices.
我们开发了一种新型全介质超表面，用于利用不对称风筝形纳米柱阵列设计高品质因子（Q因子）的连续域准束缚态（准BICs）。准BICs的Q因子遵循与几何不对称性的二次依赖关系，同时，通过与宽带磁偶极模式的相互作用，其共振光谱轮廓可以在法诺和洛伦兹线形之间轻松调整。在非线性测量中，当减小照明物镜的数值孔径时，准BIC模式的三次谐波信号在轴向长度差为15nm和75nm的样品之间表现出43.4倍至634倍的增益增强，这归因于照明光斑尺寸的增加以及大角度斜入射光对建立具有高光谱轮廓和强近场强度的准BIC模式的贡献较小。具有简单几何形状的硅基超表面便于大面积制造，并为优化上转换过程以实现高效非线性器件开辟了新的可能性。
