A harmonic vortex beam is a typical vector beam with a helical wavefront at harmonic frequencies (e.g., second and third harmonics). It provides an additional degree of freedom beyond spin- and orbital-angular momentum, which may greatly increase the capacity for communicating and encoding information. However, conventional harmonic vortex beam generators suffer from complex designs and a low nonlinear conversion efficiency. Here, we propose and experimentally demonstrate the generation of a large second-harmonic (SH) vortex beam with quasi-nonlinear spin-orbit interaction (SOI). High-quality SH vortex beams with large topological charges up to 28 are realized experimentally. This indicated that the quasi-angular-momentum of a plasmonic spiral phase plate at the excitation wavelength (topological charge, $q$) could be imprinted on the harmonic signals from the attached WS₂ monolayer. The generated harmonic vortex beam has a topological charge of $l_n=2nq$ (n is the harmonic order). The results may open new avenues for generating harmonic optical vortices for optical communications and enables novel multi-functional hybrid metasurface devices to manipulate harmonic beams.

谐波涡旋光束是典型的矢量光束，在谐波频率（例如，二次和三次谐波）下具有螺旋波前。它提供了超越自旋和轨道角动量的额外自由度，这可能会大大提高通信和编码信息的能力。然而，传统的谐波涡旋光束发生器存在设计复杂和非线性转换效率低的问题。在这里，我们提出并通过实验证明了具有准非线性自旋轨道相互作用 (SOI) 的大型二次谐波 (SH) 涡旋光束的生成。通过实验实现了具有高达 28 的大拓扑电荷的高质量 SH 涡旋光束。这表明等离子体螺旋相位板在激发波长（拓扑电荷，$q$) 可以印在附着的 WS ₂单层的谐波信号上。产生的谐波涡旋光束的拓扑电荷为${升}_n=\mathrm{2个}nq$（n是谐波次数）。结果可能为光通信产生谐波光学涡旋开辟新途径，并使新型多功能混合超表面设备能够操纵谐波光束。