Light beams with helical wave fronts, also called optical vortices, have attracted great interest in the community of optics and photonics. They provide an additional degree of freedom for light manipulation, leading to wide-ranging potential applications in micro-particle trapping, optical microscopy, and even quantum information processing. Recently, metallic microstructures are introduced to confine the plasmonic vortices into deep subwavelength dimension, which benefits photonic integration on chip. In this Letter, exploiting the excitation of spoof surface plasmon, we experimentally demonstrate the near-field optical vortices with tunable topological charges supported by a single metaparticle in the microwave regime. These microwave plasmonic-like vortices are excited by surface waves with a spatial asymmetric distribution of electromagnetic field, which are launched by a metallic comb-shaped waveguide. Experimental characterization of highly localized and controllable near-field vortices with the nature of deep subwavelength confirms the numerical simulation. In addition, an equivalent physical model based on the coupled mode theory is proposed to understand the generation mechanism of these spoof plasmonic vortices. Our approach offers an efficient way to generate deterministic subwavelength optical vortices, which provides the potential for critical vortex elements on photonic integrated chip.

中文翻译：

---

通过单个超粒子演示具有可调谐拓扑电荷的微波等离子涡旋

具有螺旋波阵面的光束，也称为光学涡旋，引起了光学和光子学界的极大兴趣。它们为光操纵提供了额外的自由度，从而在微粒捕获、光学显微镜甚至量子信息处理方面具有广泛的潜在应用。最近，金属微结构被引入以将等离子体涡旋限制在深亚波长维度，这有利于芯片上的光子集成。在这封信中，利用欺骗表面等离子体的激发，我们通过实验证明了具有可调拓扑电荷的近场光学涡流，该涡流由微波状态中的单个超粒子支持。这些类微波等离子体涡流由具有空间不对称电磁场分布的表面波激发，这些表面波由金属梳状波导发射。具有深亚波长性质的高度局部化和可控近场涡旋的实验表征证实了数值模拟。此外，提出了基于耦合模式理论的等效物理模型来理解这些欺骗等离子体涡旋的产生机制。我们的方法提供了一种生成确定性亚波长光学涡流的有效方法，这为光子集成芯片上的关键涡流元件提供了潜力。具有深亚波长性质的高度局部化和可控近场涡旋的实验表征证实了数值模拟。此外，提出了基于耦合模式理论的等效物理模型来理解这些欺骗等离子体涡的产生机制。我们的方法提供了一种生成确定性亚波长光学涡流的有效方法，这为光子集成芯片上的关键涡流元件提供了潜力。具有深亚波长性质的高度局部化和可控近场涡旋的实验表征证实了数值模拟。此外，提出了基于耦合模式理论的等效物理模型来理解这些欺骗等离子体涡的产生机制。我们的方法提供了一种生成确定性亚波长光学涡流的有效方法，这为光子集成芯片上的关键涡流元件提供了潜力。