Ultra-wideband polarization conversion metasurface based on topology optimal design and geometry tailor

We presented a topology optimization method based on genetic algorithm (GA) combined geometry tailor scheme (GTS) to realize ultra-wideband polarization conversion metasurfaces (UPCM) in microwave range. The present method takes the connectivity condition of the elements into consideration, thereby resulting in good optimization efficiency. As examples, a UPCM is designed by topology optimization, which is composed of the dielectric substrate sandwiched with patched metallic patterns and continuous metal background. Three plasmon resonances are generated by electric and magnetic resonances, which lead to bandwidth expansion of cross-polarization reflection. The simulated results show that the maximum conversion efficiency is nearly 100% at the three plasmon resonance frequencies and the 3 dB bandwidth range from 5.66 to 24.68 GHz can be achieved for both normally incident x- and y-polarized waves.