Metasurfaces have been extensively studied for generating electromagnetic waves carrying orbital angular momentum (OAM). In particular, programmable metasurfaces enable real‐time switching between multiple OAM modes in a digital manner. However, the current programmable metasurfaces are mostly based on reflective mode, which suffer from low efficiency as well as serious feed blockage. In this paper, a transmissive programmable metasurface is presented for the highly efficient generation of multimode convergent OAM beams. The proposed transmissive metasurface is composed of electronically reconfigurable units with 1‐bit phase resolution (0/π), which are obtained by integrating two PIN diodes in the radiating layer for current direction modulation. Through the antisymmetry configuration of the two PIN diodes, nearly uniform transmission magnitudes but inversed phase states in a wide band can be obtained. The simulation results show that the proposed reconfigurable unit can achieve good 1‐bit phase tuning, with minimum insertion loss of 0.2 dB and 2 dB transmission bandwidth of more than 10%. Through the dynamic modulation of the quantized code distributions on the metasurface, programmable multimode OAM beams can thus be constructed. Both simulated and measured results verify the effectiveness of the proposed design.

中文翻译：

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用于多模OAM生成的高效透射可编程超表面

对超表面进行了广泛的研究，以产生携带轨道角动量（OAM）的电磁波。特别是，可编程的超表面可实现以数字方式在多个OAM模式之间进行实时切换。然而，当前的可编程超表面主要基于反射模式，其效率低以及严重的进料阻塞。在本文中，提出了一种透射可编程超表面，用于高效产生多模会聚OAM光束。拟议的透射形超表面由具有1位相位分辨率（0 /π）的电子可重构单元组成，这些单元是通过在辐射层中集成两个PIN二极管进行电流方向调制而获得的。通过两个PIN二极管的反对称配置，可以获得几乎均匀的传输幅度，但是可以获得宽带的反相状态。仿真结果表明，所提出的可重构单元可以实现良好的1位相位调整，最小插入损耗为0.2 dB，2 dB的传输带宽超过10％。通过对超表面上的量化代码分布进行动态调制，可以构建可编程的多模OAM光束。仿真和测量结果均验证了所提出设计的有效性。因此可以构造可编程的多模OAM光束。仿真和测量结果均验证了所提出设计的有效性。因此可以构造可编程的多模OAM光束。仿真和测量结果均验证了所提出设计的有效性。