We theoretically analyze and experimentally measure the extrinsic angular momentum contribution of topologically structured darkness found within fractional vortex beams, and show that this structured darkness can be explained by evanescent waves at phase discontinuities in the generating optic. We also demonstrate the first direct measurement of the intrinsic orbital angular momentum of light with both intrinsic and extrinsic angular momentum, and explain why the total orbital angular momenta of fractional vortices do not match the winding number of their generating phases.

中文翻译：

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拓扑结构化黑暗的角动量

我们从理论上分析和实验测量了在分数涡旋光束中发现的拓扑结构化暗度的外在角动量贡献，并表明该结构化暗度可以用生成光学系统中相位不连续处的e逝波来解释。我们还展示了具有内在和外在角动量的光的本征轨道角动量的首次直接测量，并解释了为什么小数涡旋的总轨道角动量与它们产生相的绕组数不匹配的原因。