Ge Zekun, Sang Tian, Li Shi, Luo Chen, Wang Yueke
Appl Opt. 2023 Aug 1;62(22):5969-5975. doi: 10.1364/AO.495205.
For many high-precision applications such as filtering, sensing, and photodetection, active control of resonant responses of metasurfaces is crucial. Herein, we demonstrate that active control of resonant asymmetric transmission can be realized based on the topological edge state (TES) of an ultra-thin (GST) film in a photonic crystal grating (PCG). The PCG is composed of two pairs of one-dimensional photonic crystals (PCs) separated by a GST film. The phase change of the GST film re-distributes the field distributions of the PCG; thus active control of narrowband asymmetric transmission can be achieved due to the switch of the on-off state of the TES. According to multipole decompositions, the appearance and disappearance of the synergistically reduced dipole modes are responsible for the high-contrast asymmetric transmission of the PCG. In addition, the asymmetric transmission performances are robust to the variation of structural parameters, and good unidirectional transmission performances with a high peak transmission and high contrast ratio can be balanced, as the layer number of the two PCs is set as four. By changing the crystallization fraction of GST, the peak transmission and peak contrast ratio of asymmetric transmission can be flexibly tuned with the resonance locations kept almost the same.
对于许多高精度应用，如滤波、传感和光探测，超表面共振响应的主动控制至关重要。在此，我们证明基于光子晶体光栅（PCG）中超薄锗锑碲（GST）薄膜的拓扑边缘态（TES），可以实现共振非对称传输的主动控制。PCG由两对由GST薄膜隔开的一维光子晶体（PC）组成。GST薄膜的相变重新分布了PCG的场分布；因此，由于TES的开-关状态切换，可以实现窄带非对称传输的主动控制。根据多极分解，协同降低的偶极模式的出现和消失导致了PCG的高对比度非对称传输。此外，非对称传输性能对结构参数的变化具有鲁棒性，当两个PC的层数设置为四层时，可以平衡具有高峰传输和高对比度的良好单向传输性能。通过改变GST的结晶分数，可以在共振位置几乎保持不变的情况下灵活调整非对称传输的峰值传输和峰值对比度。
