Sun Zhanshan, Yang Kai, Mao Ruiqi, Lin Yi, An Qiang, Fu Yunqi
College of Electronic Science and Technology, National University of Defense Technology, Changsha, 410072, China.
Nanoscale. 2022 Jun 30;14(25):9061-9067. doi: 10.1039/d2nr00516f.
State of polarization (SoP) of light is one of the fundamental characteristics of light and has great significance to optical communication, imaging, quantum optics and medical facilities. The generation and maintenance of polarized light have always been research concerns in polarization optics. Polarization-maintaining fibers are frequently used to transmit polarized light without changing its polarization in optical systems, but the high cost and coupling efficiency problems hinder their usage in large-scale light paths. Polarization controllers, which operate arbitrary polarization generation and conversion at the expense of utilizing at least two optical elements such as a half-wave plate and quarter-wave plate, are too bulky for some special applications. Meanwhile, they can only generate desired output polarization of light by transcendentally determining the input polarization, which means that the existing polarization controllers cannot respond in real time. Metasurfaces composed of subwavelength nanoscatterers offer fruitful functionalities to manipulate the amplitude, phase and polarization of light. Here, we propose and experimentally demonstrate a real-time polarization controller realized by combining a depolarizer and polarizer into one monolithic metasurface. Arbitrary polarization states can be transferred to the required polarization with no requirement to determine the incident polarization in advance. Through combining with ordinary optical fibers, the proposed metasurface may also replace polarization-maintaining fibers and optical fiber polarizers in some polarization-dependent applications. This versatile concept may settle the problems of arbitrary polarization conversion once and for all.
光的偏振态（SoP）是光的基本特性之一，对光通信、成像、量子光学和医疗设备具有重要意义。偏振光的产生和维持一直是偏振光学领域的研究热点。保偏光纤常用于在光学系统中传输偏振光而不改变其偏振状态，但高成本和耦合效率问题限制了它们在大规模光路中的应用。偏振控制器通过使用至少两个光学元件（如半波片和四分之一波片）来实现任意偏振光的产生和转换，但其体积对于某些特殊应用来说过于庞大。同时，它们只能通过先验地确定输入偏振来生成所需的输出光偏振，这意味着现有的偏振控制器无法实时响应。由亚波长纳米散射体组成的超表面为操纵光的振幅、相位和偏振提供了丰富的功能。在此，我们提出并通过实验证明了一种将去偏振器和偏振器集成到一个整体超表面中实现的实时偏振控制器。无需预先确定入射偏振，即可将任意偏振态转换为所需的偏振态。通过与普通光纤相结合，所提出的超表面还可以在一些偏振相关的应用中替代保偏光纤和光纤偏振器。这一通用概念可能一劳永逸地解决任意偏振转换的问题。
