Achieving an ultra-narrow bandwidth analogue of electromagnetically induced transparency (EIT) in bright–bright mode coupling metasurface requires a large contrast of the Q factor and small wavelength detuning between the two coupled modes. Here, by coupling a toroidal dipole (TD) high-Q Fano resonance and a low-Q magnetic dipole (MD) mode, we numerically demonstrated a high Q factor analogue of EIT on an all-silicon metasurface in the terahertz regime. The Q factor of Fano resonance and consequent EIT can be easily adjusted by the spacing between the air holes. By adjusting the radii of the air holes, the thickness of the silicon wafer, or the lattice constant of the metasurface, EIT-like response exhibiting a very high group refractive index and a large group delay was achieved. The proposed EIT metasurface is easy to fabricate and has potential applications in the fields of narrowband filtering and slow-light based devices.

中文翻译：

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在硅太赫兹超表面中模拟具有超窄带宽的电磁感应透明度

在亮-亮模式耦合超表面中实现电磁感应透明 (EIT) 的超窄带宽模拟需要 Q 因子的大对比度和两种耦合模式之间的小波长失谐。在这里，通过耦合环形偶极子 (TD) 高 Q Fano 共振和低 Q 磁偶极子 (MD) 模式，我们在太赫兹范围内的全硅超表面上数值证明了 EIT 的高 Q 因子模拟。Fano 共振的 Q 因子和随之而来的 EIT 可以通过气孔之间的间距轻松调整。通过调整气孔的半径、硅片的厚度或超表面的晶格常数，实现了表现出非常高的群折射率和大群延迟的类 EIT 响应。