基于BIC的太赫兹全介质单向导模谐振超表面

Terahertz all-dielectric unidirectional guided resonance metasurface based on BIC

摘要:

提出一种具有高Q值的全硅结构超表面，由上下两层硅方柱构成，可通过调节上下两层结构的x方向错位距离，打破面外σz对称性，在不同晶格矢量kx处实现完美连续域束缚(BIC)态、偏振敏感的准BIC态和单向导模谐振(UGR)态的自由调控。值得注意的是，由于所提出的超表面工作在动量空间，结构对于实空间入射光的空间位置没有严格的限制。仿真结果表明，在分别打破结构几何对称性和外界入射角度对称性后，准BIC可获得10³~10⁴量级的Q值，产生的准BIC能量泄露可通过磁偶极子的不完全相消干涉解释。通过改变上下两层横向间距，可在偏离Γ点的位置实现最大单向辐射度为97.5%的单向辐射。该工作在生物化学传感、高性能通信、高效光栅耦合等领域展现出重要的应用潜力。

Abstract:

A high-Q all-silicon structured metasurface is proposed, consisting of two layers of silicon square pillars. By adjusting the lateral offset distance between the upper and lower layers in the x -direction, the out-of plane σz symmetry is broken, allowing for the free control of perfect Bound states In the Continuum(BIC) states, polarization-sensitive quasi-BIC states, and Unidirectional Guided Resonance(UGR) states at different lattice vectors kx. Notably, since the proposed metasurface operates in momentum space, there are no strict spatial position restrictions for the incident light in real space. Simulation results indicate that after breaking the structural geometric symmetry and the symmetry of the external incident angle, quasi-BIC can achieve a Q value of the order from 10³ to 10⁴. The energy leakage of the generated quasi-BIC can be explained by the incomplete destructive interference of magnetic dipoles. By changing the lateral spacing between the upper and lower layers, unidirectional radiation with a maximum unidirectional radiation efficiency of 97.5% can be achieved at off-Γ point. This work demonstrates significant application potential in the fields of biochemical sensing, high-performance communication, and efficient grating coupling.