金属周期性纳米结构的光学自旋纹理变换研究

The discovery of the optical spin textures such as optical skyrmions or merons provides a completely new idea for the light field manipulation in micro/nano scale. Topologically protected, the optical spin textures have very small size, high stability, rapidly changed polarization inside, in which the structure fineness is far beyond the optical diffraction limit. Therefore, the optical spin textures have potential applications in sub-nanometer optical displacement sensing, optical microscopic super-resolution imaging, and optical information transfer and storage. In the research before, only single skyrmion or meron is observed in a certain optical system. Based on this frontier problem, this project has a breakthrough and will observe the wavelength tuned transformation of the optical skyrmions and merons lattice. In this project, making use of the reciprocal lattice points analysis, the metallic periodic nano structure with the period satisfying certain requirements will be designed to make that the incident circular lights with different wavelength excite different optical spin textures, which will be characterized and imaged by the optical microscopic system. In addition, the preliminary research shows that the optical spin textures remain the high stability when the lattice points of the metallic periodic nano structure are randomly shifted to some extent. In this project, the mechanism of this phenomenon will be analyzed and the threshold of the randomness will be deduced. The research of this project makes the manipulation of the optical spin textures more flexible and therefore pushes the optical spin textures a step closer to their technological applications such as optical information storage.

光学斯格明子和半子等自旋纹理结构的发现为微纳尺度的光场调控提供了全新的思路，由于受到拓扑保护，它们尺寸小，稳定性高，内部偏振态变化剧烈，其结构精细度远超光学衍射极限，因此在亚纳米光学位移传感、光学超分辨显微成像、光信息存储与传输等领域具有重大应用前景。在之前的研究结果中，只在特定的光学系统观测到单一的斯格明子或半子。针对这一前沿问题，本项目有所突破，将观测波长控制的光学斯格明子和半子晶格之间的变换。本项目将利用倒格子空间分析的方法，设计周期满足特定要求的金属周期性纳米结构，使得不同波长的圆偏入射光可以激发不同的光学自旋纹理结构，并利用光学显微系统对其进行成像表征。另外，初步研究发现当金属纳米结构格点发生一定程度的随机位移时光学自旋纹理仍保持高度稳定性，本项目将对其机理进行理论分析和随机程度阈值的推导。本项目的研究令光学自旋纹理的操纵更为灵活，从而使其距离光信息存储等技术应用更近一步。

本项目主要研究金属周期性纳米结构的光学自旋纹理的变换，以解决目前存在的只在特定的光学系统观测到单一的斯格明子或半子的前沿问题。经过一年的研究工作，项目已顺利完成并达到预定目标，具体完成情况及取得成果包括：1）利用倒格子空间分析的方法，设计周期满足特定要求的金属周期性纳米结构，使得不同波长的圆偏入射光可以激发不同的光学自旋纹理结构；2）研究发现当金属纳米结构格点发生一定程度的随机位移时光学自旋纹理仍保持高度稳定性，并在理论上推导出随机程度的阈值；3）利用模拟计算为样品制备提供参数指导并成功制备样品，利用近场扫描光学显微镜完成对光学自旋纹理变换的测量并与理论计算结果相符。依托本项目共发表中科院1区论文1篇，还有1篇论文已完成尚未发表，此外还培养了出站博士后1名。本项目的研究令光学自旋纹理的操纵更为灵活，在近场光场调控和拓扑光子学等基础研究领域具有重大意义。