Polarization conversion devices are key components in spectroscopy and wireless communications systems. Conventional terahertz waveplates made of natural birefringent materials typically suffer from low efficiency, narrow bandwidth, and substantial thickness. To overcome the limitations associated with conventional waveplates, a terahertz quarter-wave metasurface with enhanced efficiency and wide bandwidth is proposed. The transmissive quarter-wave metasurface is rigorously designed based on an extended semi-analytical approach employing network analysis and genetic algorithm. Simulation results suggest that the design can achieve linear-to-circular polarization conversion with a 3-dB axial ratio relative bandwidth of 53.3%, spanning 205 GHz–354 GHz. The measurement results confirm that the proposed design enables a 3-dB axial ratio from 205 GHz to at least 340 GHz with a total efficiency beyond 70.2%, where the upper frequency bound is limited by the available experimental facility. This quarter-wave metasurface can cover an entire terahertz electronics band and can be scaled to cover other nearby bands under the same convention, which are technologically significant for future portable systems.

中文翻译：

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宽带太赫兹透射四分之一波超表面

偏振转换设备是光谱学和无线通信系统中的关键组件。由天然双折射材料制成的常规太赫兹波片通常具有效率低，带宽窄和厚度大的缺点。为了克服与传统波片相关的局限性，提出了一种具有增强的效率和宽带宽的太赫兹四分之一波超颖表面。透射式四分之一波长超颖表面是基于采用网络分析和遗传算法的扩展半分析方法而严格设计的。仿真结果表明，该设计可以在205 GHz至354 GHz的频率范围内以3-dB的轴向比率相对带宽为53.3％的情况实现线性至圆极化转换。测量结果证实，该提议的设计实现了从205 GHz到至少340 GHz的3 dB轴向比率，总效率超过70.2％，其中上限频率受到可用实验设备的限制。这个四分之一波的超表面可以覆盖整个太赫兹电子频段，并且可以按照相同的约定进行缩放以覆盖其他附近的频段，这在未来的便携式系统中具有重要的技术意义。