• 摘要: 光学斯格明子为实现结构光场以及时空光场的拓扑属性提供了新的研究方法与研究思路。本文在4π聚焦系统中,通过对两对入射柱矢量光束进行偏振与相位调控,实现了聚焦光场纵向分量与横向分量的独立控制,在焦平面上得到了Néel型与Bloch型的电磁矢量光学斯格明子。在4π聚焦系统内调控两对反向传播的径向偏振光时,焦平面处将产生Néel型的电场矢量斯格明子。将其中一对替换为角向偏振光时,焦平面处将同时产生Bloch型的电场矢量斯格明子与相位超前π/2的磁场矢量斯格明子。本工作为进一步研究自由空间中微纳尺度电磁矢量光学斯格明子与物质的相互作用提供了理论基础。

       

      Abstract: Optical skyrmions provide a new idea and approach to endow structured light and spatial-temporal light with topological properties. In this paper, the longitudinal and transversal components of the focused light field are decoupled and can be controlled independently by modulating the polarizations and phases of two pairs of counter-propagating incident cylindrical vector beams under 4π focal configuration. Under this condition, Néel-type and Bloch-type optical skyrmions formed by electromagnetic field vectors are constructed in the focal plane. When one pair of the incident beams is radially polarized with a phase difference of π and the other pair is radially polarized in phase, a Néel-type optical skyrmion formed by electric field vectors can be constructed in the focal plane of the 4π focal system. The corresponding focal magnetic field is purely azimuthally polarized. If we substitute the other pair of the incident beams with azimuthally polarized beams, Bloch-type optical skyrmions formed by electromagnetic field vectors can be constructed in the focal plane, where the one formed by magnetic field vectors has a π/2 phase lead compared with the that formed by electric field vectors. This work provides a theoretical basis for further research on the interactions between matter and optical skyrmions formed by electromagnetic field vectors at micro and nano scales in free space.