We study an independently tunable Fano resonance from quasibound state in the continuum and polarization-independent toroidal dipole resonance in hybrid graphene–dielectric metasurface consisting of a nanoring and a cross-shaped nanobar. The unique structural properties of the proposed metasurface can support directional toroidal dipole mode, where the asymmetric magnetic field enhancement can be dynamically switched on and off while maintaining polarization-independent Fano spectral response. Through reducing or increasing inner radius of nanoring, an additional quasi-BIC dominated by magnetic dipole moment can be excited and independently tuned by altering the polarization direction of the incident wave. In addition, the quasi-BIC can be effectively modulated via adjusting the Fermi energy and layer numbers of the graphene. Our results can be of practical interest for a variety of applications including optical modulator, filter, switches, and light trapping.

中文翻译：

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用于磁场可调性的混合石墨烯-电介质超表面连续体中准束缚态的独立可调 Fano 共振

我们研究了连续体中准束缚态的独立可调 Fano 共振和由纳米环和十字形纳米棒组成的混合石墨烯-电介质超表面中的偏振无关环形偶极子共振。所提出的超表面的独特结构特性可以支持定向环形偶极子模式，其中可以动态打开和关闭不对称磁场增强，同时保持与偏振无关的 Fano 光谱响应。通过减小或增加纳米环的内半径，可以激发额外的由磁偶极矩主导的准 BIC，并通过改变入射波的偏振方向进行独立调谐。此外，通过调整石墨烯的费米能量和层数可以有效地调制准BIC。