While spin–orbit interaction has been extensively studied, few investigations have reported on the interaction between orbital angular momenta (OAMs). In this work, we study a new type of orbit–orbit coupling between the longitudinal OAM and the transverse OAM carried by a three-dimensional (3D) spatiotemporal optical vortex (STOV) in the process of tight focusing. The 3D STOV possesses orthogonal OAMs in the x–y, t–x, and y–t planes, and is preconditioned to overcome the spatiotemporal astigmatism effect. x, y, and t are the axes in the spatiotemporal domain. The corresponding focused wavepacket is calculated by employing the Debye diffraction theory, showing that a phase singularity ring is generated by the interactions among the transverse and longitudinal vortices in the highly confined STOV. The Fourier-transform decomposition of the Debye integral is employed to analyze the mechanism of the orbit–orbit interaction. This is the first revelation of coupling between the longitudinal OAM and the transverse OAM, paving the way for potential applications in optical trapping, laser machining, nonlinear light-matter interactions, and more.

中文翻译：

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时空光学涡旋中的轨道-轨道相互作用


虽然自旋-轨道相互作用已被广泛研究，但很少有研究报道轨道角动量 （OAM） 之间的相互作用。在这项工作中，我们研究了三维 （3D） 时空光学涡旋 （STOV） 在紧密聚焦过程中纵向 OAM 和横向 OAM 之间的一种新型轨道-轨道耦合。3D STOV 在 x-y、t-x 和 y-t 平面上具有正交 OAM，并经过预处理以克服时空散光效应。x、y 和 t 是时空域中的轴。采用德拜衍射理论计算了相应的聚焦波包，表明相位奇异性环是由高度受限的 STOV 中横向和纵向涡旋之间的相互作用产生的。采用 Debye 积分的傅里叶变换分解来分析轨道-轨道相互作用的机制。这是纵向 OAM 和横向 OAM 之间耦合的首次揭示，为光捕获、激光加工、非线性光-物质相互作用等潜在应用铺平了道路。