Cao Shulei, Du Luping, Shi Peng, Yuan Xiaocong
Opt Express. 2024 Jan 29;32(3):4167-4179. doi: 10.1364/OE.514440.
The recent emerging appearance of optical analogs of magnetic quasiparticles, i.e., optical skyrmions constructed via spin, field, and Stokes vectors, has garnered substantial interest from deep-subwavelength imaging and quantum entanglement. Here, we investigate systematically the topological state transitions of skyrmionic beams constructed by the Stokes vectors in the focusing configuration. We theoretically demonstrated that in the weak focusing, the skyrmion topological number is protected. Whereas, in the tight focusing, a unique topological transformation with skyrmion number variation is exhibited for the optical skyrmion, anti-skyrmion, and 2-order skyrmion structures. The significant difference between the topological state transitions of these two cases originates from the transformation from the paraxial optical system to the nonparaxial optical system, and the approximate two-dimensional polarization structure to the three-dimensional polarization structure. The results provide new insights into the topological state transitions in topological structures, which promote applications in information processing, data storage, and free-space optical communications.
磁性准粒子的光学类似物，即通过自旋、场和斯托克斯矢量构建的光学斯格明子，最近的出现引起了深亚波长成像和量子纠缠领域的广泛关注。在此，我们系统地研究了在聚焦配置下由斯托克斯矢量构建的斯格明子光束的拓扑态转变。我们从理论上证明，在弱聚焦情况下，斯格明子拓扑数是受保护的。然而，在紧聚焦情况下，光学斯格明子、反斯格明子和二阶斯格明子结构表现出具有斯格明子数变化的独特拓扑转变。这两种情况的拓扑态转变之间的显著差异源于从傍轴光学系统到非傍轴光学系统的转变，以及从近似二维偏振结构到三维偏振结构的转变。这些结果为拓扑结构中的拓扑态转变提供了新的见解，有助于推动其在信息处理、数据存储和自由空间光通信中的应用。
