Bound states in the continuum (BICs) spectrum are localized states in the continuum domain with an infinite lifetime, zero radiation, and an infinite quality factor (Q-factor). The structural symmetry is typically broken to transform BICs into quasi-BICs with ultrahigh Q-factors, which are used in fields such as optical switches, nonlinear optics, and sensing. Herein, we present an all-dielectric metasurface fabricated by depositing Si on the SiO₂ substrate and etching an “8”-shape hole in the middle of each unit. By breaking the symmetry of the structure, the BIC is transformed into a quasi-BIC mode, which can realize triple Fano resonances with a high Q-factor. The effects of different structural parameters on the Fano resonances are investigated by varying the structural parameters. The physical mechanisms of the three Fano resonances are elucidated by combining the electromagnetic field and multipole decomposition of scattered power. Calculation results show that the maximum Q-factor reaches 4.7 × 10⁴, the maximum figure-of-merit (FOM) value reaches 675, and the modulation depths of the three resonances are approximately 100%. The metasurface exhibits a high Q-factor, FOM value, and modulation depth, thus rendering it suitable for application to high-performance biosensors, nonlinear optics, and optical switches.

连续谱 (BIC) 谱中的束缚态是连续域中的局域态，具有无限寿命、零辐射和无限品质因数 (Q 因子)。通常会破坏结构对称性，将 BIC 转变为具有超高 Q 因子的准 BIC，用于光开关、非线性光学和传感等领域。在此，我们提出了一种全介电超表面，通过在 SiO ₂基板上沉积 Si 并在每个单元的中间蚀刻“8”形孔来制造。通过打破结构的对称性，BIC转变为准BIC模式，可以实现高Q值的三法诺共振。通过改变结构参数来研究不同结构参数对法诺共振的影响。通过结合电磁场和散射功率的多极分解，阐明了三种法诺共振的物理机制。计算结果表明，最大Q值达到4.7×10 ⁴，最大品质因数(FOM)值达到675，三个谐振的调制深度接近100%。该超表面具有高Q因子、FOM值和调制深度，因此适合应用于高性能生物传感器、非线性光学和光开关。