Chen Shiwen, Zeng Yixuan, Li Zhongfu, Mao Yu, Dai Xiaoyu, Xiang Yuanjiang
School of Physics and Electronics, Hunan University, Changsha 410082, China.
Ministry of Industry and Information Technology Key Lab of Micro-Nano Optoelectronic Information System, Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen, 518055 P. R. China.
Nanophotonics. 2023 Aug 8;12(18):3613-3621. doi: 10.1515/nanoph-2023-0319. eCollection 2023 Sep.
Free-space nonreciprocal transmission is a crucial aspect of modern optics devices. The implementation of nonreciprocal optical devices through optical nonlinearity has been demonstrated. However, due to the weak nonlinearity of traditional materials, most self-biased nonreciprocal devices are heavily dependent on the high strong resonances. In general, these resonances are frequently polarization sensitive. In this work, we propose ultrathin optical metasurface embedding Kerr nonlinearities to achieve nonreciprocal transmission and optical bistability for free-space propagation based on symmetry-protected bound states in the continuum (BICs). Since the structure of the metasurface retains C symmetry, the symmetry-protected BIC is polarization-independent. It is also shown that the nonreciprocal intensity range could be largely tuned by the structure parameters. The demonstrated devices merge the field of nonreciprocity with ultrathin metasurface technologies making this design an exciting prospect for an optical switch, routing, and isolator with optimal performance.
自由空间非互易传输是现代光学器件的一个关键方面。通过光学非线性实现非互易光学器件的方法已经得到了证明。然而，由于传统材料的非线性较弱，大多数自偏置非互易器件严重依赖于高 强共振。一般来说，这些共振通常对偏振敏感。在这项工作中，我们提出了一种嵌入克尔非线性的超薄光学超表面，以基于连续统中的对称保护束缚态（BICs）实现自由空间传播的非互易传输和光学双稳性。由于超表面的结构保留了C对称性，对称保护的BIC与偏振无关。研究还表明，非互易强度范围可以通过结构参数进行很大程度的调节。所展示的器件将非互易性领域与超薄超表面技术相结合，使得这种设计成为具有最佳性能的光开关、路由和隔离器的一个令人兴奋的前景。
