In this Letter, we propose an approach to generate high-purity orbital angular momentum (OAM) vortex waves using an amplitude-and-phase metasurface (APM). By varying the square split ring opening and orientation angles, the cross-polarized reflection response of the proposed structure can yield full phase and amplitude coverage. Based on the traditional phase-only metasurface (POM), the Chebyshev synthesis method (CSM) is applied to array the metasurface amplitude distribution. Metasurfaces with modes $l$ of 1, 2, 3, and 4 are designed. Compared with the POM, the APM can effectively improve the vortex beam quality and OAM mode purity. The measured results agree well with full-wave simulations. The presented method provides a new, to the best of our knowledge, way to design high-purity OAM generators based on metasurfaces.

中文翻译：

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使用振幅和相位超表面的高纯度轨道角动量涡旋光束发生器

在这封信中，我们提出了一种使用振幅相位超表面 (APM) 产生高纯度轨道角动量 (OAM) 涡旋波的方法。通过改变方形裂环开口和取向角，所提出结构的交叉极化反射响应可以产生全相位和幅度覆盖。在传统的仅相位超表面（POM）的基础上，应用切比雪夫合成方法（CSM）对超表面幅度分布进行阵列。具有模式$l$ 的超表面设计了 1、2、3 和 4。与POM相比，APM可以有效提高涡旋光束质量和OAM模式纯度。测量结果与全波模拟非常吻合。据我们所知，所提出的方法提供了一种新的方法来设计基于超表面的高纯度 OAM 发生器。