The spin–orbit interaction and the extrinsic orbit–orbit interaction of light have been thoroughly studied, which have led to important phenomena including the spin Hall effect, orbital Hall effect, and spin–orbit Hall effect of light. Nevertheless, the concept of optical intrinsic orbit–orbit interaction, which is named as vortex–antivortex interaction, is scarcely known to the authors knowledge. Here, such a novel interaction process is theoretically and experimentally demonstrated, which emerges due to mutual interplays among reciprocal helicities of singular cores in a freely propagating light field. A general model describing the process is presented, which includes a linearly independent term and a nonlinearly coupling term. It is revealed that the strong coupling leads to intuitive mutual attraction between two reciprocal vortices, while the weak coupling, in contrast, results in a counterintuitive repulsive phenomenon. The vortex–antivortex interaction enables the predictions and observations of the orbital angular momentum Hall effect, as well as the stable propagation of an appropriately structured vortex arrays without nonlinear light–matter interactions. The results expand the scope of interaction processes among different forms of optical angular momenta, and open opportunities for studies of new effects using the presented coupling mechanism.

中文翻译：

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光的本征涡旋-反涡旋相互作用

对光的自旋-轨道相互作用和外在轨道-轨道相互作用进行了深入研究，从而产生了光的自旋霍尔效应、轨道霍尔效应和自旋轨道霍尔效应等重要现象。然而，光学本征轨道-轨道相互作用的概念，即涡旋-反涡旋相互作用，作者所知甚少。在这里，这种新颖的相互作用过程在理论上和实验上都得到了证明，这是由于在自由传播的光场中奇异核的互易螺旋性之间的相互作用而出现的。提出了描述该过程的一般模型，其中包括线性独立项和非线性耦合项。揭示了强耦合导致两个互惠涡旋之间直观的相互吸引，相比之下，弱耦合会导致违反直觉的排斥现象。涡旋-反涡旋相互作用能够预测和观察轨道角动量霍尔效应，以及结构适当的涡旋阵列在没有非线性光-物质相互作用的情况下的稳定传播。结果扩大了不同形式的光学角动量之间相互作用过程的范围，并为使用所提出的耦合机制研究新效应开辟了机会。