In this letter, a method for generating low‐sidelobe orbital angular momentum (OAM) beam is presented using a donut‐shaped amplitude and phase metasurface (DS‐APM). Building upon conventional phase‐only metasurface, the Bayliss synthesis method is employed to adjust the amplitude distribution on the metasurface. Thereby, the amplitude and phase metasurface (APM) can reduce the sidelobe level of the OAM beam. Subsequently, considering the Nyquist conditions and momentum constraints, a hollow modification is implemented on the APM array aperture center. The adjustment of the hollow dimension renders the DS‐APM compatible with the corresponding OAM beam mode number. Furthermore, a modified I‐shaped element is proposed, which enables independent modulation of the amplitude and phase of reflected cross‐polarized waves. Utilizing the proposed elements, a DS‐APM applied to generate a second‐order OAM beam operating at 15 GHz was designed, fabricated, and measured. The measurement results align with the full‐wave simulations, thereby validating the rationality of the proposed method.

中文翻译：

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基于Bayliss合成法的环形振幅相位超表面低旁瓣轨道角动量束

在这封信中，提出了一种使用环形振幅和相位超表面（DS-APM）生成低旁瓣轨道角动量（OAM）光束的方法。在传统的仅相位超表面的基础上，采用贝利斯合成方法来调整超表面上的幅度分布。因此，幅度和相位超表面（APM）可以降低OAM光束的旁瓣电平。随后，考虑奈奎斯特条件和动量约束，对APM阵列孔径中心进行空心修改。中空尺寸的调整使得DS-APM与相应的OAM光束模数兼容。此外，还提出了一种改进的 I 形元件，它能够独立调制反射的交叉偏振波的幅度和相位。利用所提出的元件，设计、制造和测量了用于生成工作频率为 15 GHz 的二阶 OAM 光束的 DS-APM。测量结果与全波模拟一致，从而验证了所提方法的合理性。