Ji Wenye, Cai Tong, Wang Guangming, Li Haipeng, Wang Canyu, Hou Haisheng, Zhang Chiben
Opt Express. 2019 Feb 4;27(3):2844-2854. doi: 10.1364/OE.27.002844.
Achieving asymmetric transmission effects, especially in an ultra-broadband frequency region, is of particular importance in communication systems. Currently available asymmetric transmission metasurfaces are limited to narrow bands and low efficiencies because of the inherently dispersion effects and large transmission fluctuations. In this paper, we propose a new strategy to realize high efficiency and ultra-broadband asymmetric transmission in an ultra-thin profile by using the topologically coding optimization method. The meta-atom consists of two outer orthogonal gratings and a central lattice particle optimized by genetic algorithm. The optimized central lattice suppresses the transmission fluctuations by tuning the coupling among different metallic layers, resulting in very broad band and high transmissions. Experimental results show that our metasurface achieved perfect reflection over 95% and high cross-polarization transmission over 80% for y- and x-polarized incidence from 5.3 GHz to 16.7 GHz, respectively. Our findings pave a way to high-performance and broadband polarization transformers and polarization-controlled devices working in different frequency domains.
实现非对称传输效应，尤其是在超宽带频率区域内，在通信系统中具有特别重要的意义。由于固有的色散效应和较大的传输波动，目前可用的非对称传输超表面仅限于窄带且效率较低。在本文中，我们提出了一种新策略，通过使用拓扑编码优化方法在超薄外形中实现高效和超宽带非对称传输。元原子由两个外部正交光栅和一个通过遗传算法优化的中心晶格粒子组成。优化后的中心晶格通过调整不同金属层之间的耦合来抑制传输波动，从而实现非常宽的带宽和高传输率。实验结果表明，我们的超表面对于从5.3 GHz到16.7 GHz的y偏振和x偏振入射，分别实现了超过95%的完美反射和超过80%的高交叉极化传输。我们的研究结果为高性能和宽带偏振变压器以及在不同频域工作的偏振控制设备铺平了道路。
