Zhang Lijuan, Wang Chengmiao, Wei Yupei, Lin Yu, Han Yeming, Deng Yongbo
Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP), Chinese Academy of Sciences, Changchun 130033, China.
University of Chinese Academy of Sciences, Beijing 100039, China.
Nanomaterials (Basel). 2023 Feb 27;13(5):890. doi: 10.3390/nano13050890.
Metalens, composed of arrays of nano-posts, is an ultrathin planar optical element used for constructing compact optical systems which can achieve high-performance optical imaging by wavefront modulating. However, the existing achromatic metalenses for circular polarization possess the problem of low focal efficiency, which is caused by the low polarization conversion efficiencies of the nano-posts. This problem hinders the practical application of the metalens. Topology optimization is an optimization-based design method that can effectively extend the degree of design freedom, allowing the phases and polarization conversion efficiencies of the nano-posts to be taken into account simultaneously in the optimization procedures. Therefore, it is used to find geometrical configurations of the nano-posts with suitable phase dispersions and maximized polarization conversion efficiencies. An achromatic metalens has a diameter of 40 μm. The average focal efficiency of this metalens is 53% in the spectrum of 531 nm to 780 nm by simulation, which is higher than the previously reported achromatic metalenses with average efficiencies of 20~36%. The result shows that the introduced method can effectively improve the focal efficiency of the broadband achromatic metalens.
超构透镜由纳米柱阵列组成，是一种超薄平面光学元件，用于构建紧凑的光学系统，该系统可通过波前调制实现高性能光学成像。然而，现有的用于圆偏振的消色差超构透镜存在聚焦效率低的问题，这是由纳米柱的低偏振转换效率导致的。这个问题阻碍了超构透镜的实际应用。拓扑优化是一种基于优化的设计方法，它可以有效地扩展设计自由度，使纳米柱的相位和偏振转换效率在优化过程中同时得到考虑。因此，它被用于寻找具有合适相位色散和最大化偏振转换效率的纳米柱几何构型。一个消色差超构透镜的直径为40μm。通过模拟，该超构透镜在531nm至780nm光谱范围内的平均聚焦效率为53%，高于先前报道的平均效率为20%至36%的消色差超构透镜。结果表明，所引入的方法可以有效地提高宽带消色差超构透镜的聚焦效率。
