Optical singularity states, which significantly affect propagation properties of light in free space or optical medium, can be geometrically classified into screw and edge types. These different types of singularity states do not exhibit direct connection, being decoupled from each other in the absence of external perturbations. Here we demonstrate a novel optical process in which a higher-order edge singularity state initially nested in the propagating Gaussian light field gradually involves into a screw singularity with a new-born topological charge determined by order of the edge state. The considered edge state comprises an equal superposition of oppositely charged vortex and antivortex modes. We theoretically and experimentally realize this edge-to-screw conversion process by introducing intrinsic vortex–antivortex interaction. We also present a geometrical representation for mapping this dynamical process, based on the higher-order orbital Poincaré sphere. Within this framework, the edge-to-screw conversion is explained by a mapping of state evolution from the equator to the north or south pole of the Poincaré sphere. Our demonstration provides a novel approach for manipulating singularity state by the intrinsic vortex–antivortex interactions. The presented phenomenon can be also generalized to other wave systems such as matter wave, water wave, and acoustic wave.

中文翻译：

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光学边缘到螺旋奇点状态转换


光学奇点态显着影响光在自由空间或光学介质中的传播特性，在几何上可以分为螺旋型和边缘型。这些不同类型的奇点状态不表现出直接联系，在没有外部扰动的情况下彼此解耦。在这里，我们演示了一种新颖的光学过程，其中最初嵌套在传播高斯光场中的高阶边缘奇点状态逐渐进入螺旋奇点，并具有由边缘状态的阶数决定的新生拓扑电荷。所考虑的边缘状态包括带相反电荷的涡旋和反涡旋模式的相等叠加。我们通过引入本征涡旋-反涡旋相互作用，在理论上和实验上实现了这种边缘到螺杆的转换过程。我们还提出了基于高阶轨道庞加莱球的几何表示，用于绘制这一动态过程。在这个框架内，边缘到螺旋的转换是通过从赤道到庞加莱球的北极或南极的状态演化图来解释的。我们的演示提供了一种通过本征涡旋-反涡旋相互作用来操纵奇点状态的新方法。所提出的现象也可以推广到其他波系，例如物质波、水波和声波。