Topology optimization of the azimuth-rotation-independent polarization conversion metasurface for bandwidth enhancement
Gong Cheng, Liming Si, Pengcheng Tang, Yaqiang Zhuang, Houjun Sun, Jun Ding
Abstract
Metasurfaces offer an unprecedented opportunity for flexible manipulation of electromagnetic wave. The azimuth-rotation-independent (ARI) polarization conversion metasurface (PCM) is an ultrathin device, which could convert an arbitrary linearly-polarized incident wave to its cross-polarized state. However, the bandwidth of an ARI PCM with a high cross-polarized transmission is usually limited. Here, a topology optimization method of multi-feature points based on the differential evolution (DE) algorithm is adopted to enhance the bandwidth of the traditional ARI PCM while maintaining a high transmission and polarization conversion ratio. The simulated results of the optimized structure indicate a 2.08 times bandwidth expansion in the cross-polarization conversion compared with the original structure. In addition, the measured results are consistent with the simulated ones and the ARI characteristic is validated. The proposed method provides a promising route for efficient high-performance metasurface designs.