半导体微腔中激子-极化激元涡旋的产生与操控的研究

The study of two-dimensional materials and semiconductor devices are important and hot research topics in recent decades, because their novel properties show promising application in many fields. Recently, scholars pay more attention to the study of a new quasi-particle, exciton-polariton, in semiconductor microcavities. The quasi-2D motion and their ultra-fast lifetime and extremely small effective mass of polaritons make semiconductor devices having great advantages in the field of all-optical control and information processing. The existence of a vortex in polaritons have been proved in the previous study. People found a complicated method to choose a certain topological charge of a vortex. This kind of topological charge control is demonstrated useful in the field of all-optical control and information processing. However, the complicated control is hard to achieve in reality, and the external disorder and noise can easily destroy a vortex. These are two main difficulties at present in the study of vortices and their control. In this project, we will search for more stable and much easier methods to control the topological charges of vortices. Namely, a coupled vortex pair shows periodic oscillation when they are close to each other. An incoherent pulse then can be used to switch a vortex between different topological charges. To stabilize a vortex, one can fabricate an external potential in the semiconductor microcavity. This potential should have the similar shape of a vortex. Meanwhile, in this project we will also study the existence of double-ring vortices and the bistability, vortex and non-vortex states, of polaritons. We have demonstrated the stability of vortices and their topological control, including single vortex and multi vortices, in our previous study, as well as the influence of a potential on the dynamics of polaritons. These experience are very helpful for our current project.

二维材料和半导体器件一直是科学研究的热点，因为它们的特殊性质有着广泛的应用前景。近几年，半导体微腔中的准二维粒子——激子-极化激元受到学者们的青睐，因为其超快的响应和极小的有效质量使以该粒子为载体的准二维半导体器件在全光开关和信息存储等领域有着非常大的优势。之前的研究证实了极化激元涡旋态的存在以及对涡旋拓扑电荷较为复杂的控制，以此来实现全光操控和信息处理。然而过于复杂的操控以及由于外界干扰所导致的不稳定性是目前最大的两个难题。本项目将探索更加简单而且稳定的控制方法，即通过相位锁定的涡旋实现周期震荡，然后由一束非相干脉冲光来实现对涡旋的控制；为了使涡旋更加稳定，需要外部势阱对其进行约束。本项目还将对双环涡旋进行研究，探索涡旋和非涡旋的双稳态。之前的研究中我们验证了涡旋的稳定性，实现了对单个涡旋以及多个涡旋的控制，研究了外部势阱对极化激元的影响，这对本项目的开展以及实现预期目标有非常大的帮助。

近年来，微腔光子学备受学者们青睐，尤其是通过不同的微腔结构来实现对光子的控制。半导体微腔中的光子还可以通过和半导体材料中的激子相互作用形成新型准粒子：激子-极化激元。极化激元具有超快的响应和极小的有效质量，并且表现出非常强的非线性特性。作为非线性特性之一，在本项目开展之前，涡旋在极化激元系统中已经被初步地研究并报道。本项目对极化激元中涡旋的产生与操控进行了详细的理论研究，经过三年研究，我们对如何激发特定结构的涡旋以及对涡旋拓扑电荷的调控有了深入的了解，对以涡旋为载体的光学双稳态有了新的认识，在理论方面取得了一些进展，主要成果包括：..1）在光学势阱和外部势阱中都实现了涡旋的光学双稳态。..2）提出了对涡旋拓扑电荷的简易操控，并在实验上得以实现。..3）研究了自旋轨道耦合对半涡旋的影响以及对半涡旋中拓扑电荷的控制。..4）成功构建了嵌套环状势阱中拥有不同传输方向的极化激元流。..5）在PT对称的势阱中发现了能快速传输的极化激元波包。..这些结果进一步揭示了微腔极化激元奇特的物理以及非线性特性，发掘了极化激元在信息处理和数据存储等领域的潜在应用。本项目的开展以及成果都和预期目标非常相符。在此期间，共发表论文10篇，其中一区文章2篇，二区文章8篇。