Polarization is a crucial characteristic of electromagnetic fields, and the ability to fully control it has many useful applications. While novel nanophotonic devices have been designed to achieve unprecedented capability to manipulate light on demand, their usage in the complete control of polarization states for the transmitted light has been relatively limited, and traditional design methods always produce devices with narrow operation bandwidths. In this work, a two-phase topology optimization strategy is proposed in conjunction with adjoint method to inverse design photonic crystal slabs capable of complete polarization control. It successfully produces devices operating over a broad bandwidth that is significantly larger than the current state-of-the-art designs, and their performances are also robust to material loss. This is also find that the C_2v symmetry of the structure can regularize the problem, so that less simulation time and faster convergence can be obtained without compromising performance. This study demonstrates the power of the inverse design method, which can be further applied to achieve more complex polarization control and beyond.

中文翻译：

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通过反向设计的光子晶体板实现宽带完整偏振控制

极化是电磁场的一个重要特性，完全控制它的能力有许多有用的应用。虽然新颖的纳米光子器件被设计为实现前所未有的按需操纵光的能力，但它们在完全控制透射光的偏振态方面的用途相对有限，并且传统的设计方法总是产生具有窄操作带宽的器件。在这项工作中，提出了一种两相拓扑优化策略，结合伴随方法来逆向设计能够完全偏振控制的光子晶体板。它成功地生产了在比当前最先进的设计大得多的宽带宽上运行的设备，并且它们的性能对于材料损失也具有鲁棒性。这还发现结构的C _{2 v}对称性可以使问题正则化，从而在不影响性能的情况下获得更少的模拟时间和更快的收敛。这项研究展示了逆向设计方法的强大功能，可以进一步应用该方法来实现更复杂的偏振控制及其他功能。