Perfect (optical) vortex (PV) beams are fields whose radial profile is mooted to be independent of orbital angular momentum (OAM). To date, the best experimental approximation of these modes is obtained from passing Bessel–Gaussian beams through a Fourier lens. However, the OAM-dependent width of these quasi-PVs is not precisely known and is often understated. We address this here by deriving and experimentally confirming an explicit analytic expression for the second moment radius of quasi-PVs. We show that this width scales in proportion to $\sqrt{\ell }$ in the best case, the same as most “regular” vortex modes, albeit with a much smaller proportionality constant. This Letter will be of interest to the large community who seek to use such structured light fields in various applications, including optical trapping, tweezing, and communications.

中文翻译：

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完美的涡旋光束有多完美？

理想（光学）涡旋（PV）束是其径向轮廓必须独立于轨道角动量（OAM）的场。迄今为止，通过使贝塞尔-高斯光束通过傅立叶透镜可以获得这些模式的最佳实验近似值。但是，这些准PV的依赖于OAM的宽度尚不清楚，并且经常被低估。我们在这里通过推导和实验确定准PVs的第二矩半径的显式解析表达式来解决此问题。我们显示此宽度与$\sqrt{\ell }$在最佳情况下，与大多数“常规”涡旋模式相同，尽管比例常数要小得多。寻求在各种应用中使用这种结构化光场的广大社区将对这封信感兴趣，这些应用包括光学陷波，镊子和通信。