超表面是一种亚波长阵列人工微纳结构，因其特殊的电磁谐振效应而具有一些天然材料所不具备的新颖的电磁特性，如波前调控和异常透射等。偏振是电磁波的标志之一，偏振态的电磁波在无线通信，成像，传感等领域起到了非常重要的作用。近年来，越来越多的科研人员投身于超表面偏振态调控的研究中。超表面由于其具有低损耗、宽带响应、超薄、尺寸小易集成等诸多优点，利用超表面结构产生偏振态电磁波在偏振成像探测、生物传感、量子通信等诸多偏振调控相关领域都有着巨大的应用前景。本文所做主要工作是研究超表面结构的正交偏振转换机理，首先设计并研究了一种五层金属超表面结构，实现了蓝光波段入射光的非对称传输；为了实现自然光入射，特定线偏振光的透射率大于50%，又设计并研究了一种三层金属超表面结构，实现了蓝光波段入射光的非对称偏振转换；在前两种结构基础上，为了进一步提高器件的偏振转换性能，设计并研究了高透射高偏振转换的双层介质超表面，并利用时域有限差分法计算并分析了以上三种超表面结构的器件性能和内在机理。本论文相关研究内容如下：

（1）通过文献调研，研究并分析了国内外金属/介质超表面的研究现状，详细描述了金属/介质超表面的偏振调控特性以及内在机理。

（2）设计了一种基于正交金属栅的蓝光波段非对称传输超表面结构，实现了对正入射线偏振光的非对称传输，对入射线偏光的交叉偏振透射率峰值达到68%左右。对超表面结构进行了仿真计算和性能分析，研究了该结构的非对称传输性能。通过建立类法布里珀罗腔模型，为高偏振转换非对称传输的形成提供了明确的解释机制，并优化了主要结构参数。

（3）设计了一种金属双杆和金属栅耦合的蓝光波段非对称偏振转换超表面结构，实现了对特定线偏振光的高透过，而对其正交线偏振光进行偏振转换，使得在自然光入射条件下，特定线偏光的透过率大于50%。对超表面结构进行了仿真计算和性能分析，研究了该结构的非对称偏振转换性能。基于谐振波长处的表面电流分布，分析了该结构产生高效率非对称偏振转换的内在机理，证明了该结构能实现自然光入射，特定线偏光的透过率大于50%。最后结合深度学习来寻找全局最优的结构参数，进一步优化了器件性能。

（4）设计了一种基于全介质双杆的单位转换效率偏振转换超表面结构，实现了正入射线偏振光接近100%的偏振转换效率。对超表面结构进行了仿真计算和性能分析，研究了它的结构性能。分析了该全介质超表面能够实现近100% 偏振转换的基本原理。通过多极分解对谐振波长处超表面结构的高透过率和高偏振转换进行了研究，并优化了主要结构参数。

（5）总结本论文提出的超表面结构的研究内容，并展望将来可以通过全介质超表面结构来实现更高的非对称偏振调控效率，进一步提高偏振调控器件的性能。

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