Full control of dual-band vortex beams using a high-efficiency single-layer bi-spectral 2-bit coding metasurface
Full control of dual-band vortex beams using a high-efficiency single-layer bi-spectral 2-bit coding metasurface
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DOI：
10.1364/oe.394571
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发表时间：
2020-06-08
期刊：
影响因子：
3.8
通讯作者：
Ding, Jun
中科院分区：
文献类型：
--
作者：
Xin, Mingbo;Xie, Rensheng;Ding, Jun
携带轨道角动量（OAM）模式的涡旋光束（VB）已被证明是增加通信容量的有前途的资源。尽管基于元表面的VB生成器由于其前所未有的优势而受到了相当大的关注，但大多数应用通常局限于具有固定OAM模式的单个频带。在这项工作中，提出了一种新兴的双频带反射型编码元表面，以缓解这些问题，新设计的元原子，它可以实现独立的2位相位调制在两个频带。所提出的编码元表面可以有效地实现并完全控制线偏振入射下的双频带携带频率选择性OAM模式的VB。作为第一个说明性的例子，一个双波段VB发生器与正常的光束方向的制造和特点，在两个广泛使用的通信频段（Ku和Ka波段）。此外，通过对适当的编码序列进行编码，可以实现携带频率选择性OAM模式的通用波束。因此，通过将梯度相位序列添加到第一VB发生器，第二VB发生器被设计为将所生成的波束引导到预设方向，这可以实现不同的场景。两个VB发生器的测量结果与数值结果吻合得很好，验证了所提出的方法的完全控制能力。(C)根据OSA开放获取出版协议的条款，2020年美国光学学会
Vortex beams (VBs) carrying orbital angular moment (OAM) modes have been proven to be promising resources for increasing communication capacity. Although considerable attention has been paid on metasurface-based VB generators due to the unprecedented advantages of metasurface, most applications are usually limited at a single band with a fixed OAM mode. In this work, an emerging dual-band reflection-type coding metasurface is proposed to mitigate these issues by newly engineered meta-atoms, which could achieve independent 2-bit phase modulations at two frequency bands. The proposed coding metasurface could efficiently realize and fully control dual-band VBs carrying frequency selective OAM modes under the linearly polarized incidence. As the first illustrative example, a dual-band VB generator with normal beam direction is fabricated and characterized at two widely used communication bands (Ku and Ka bands). Moreover, by encoding proper coding sequences, versatile beams carrying frequency selective OAM modes can be achieved. Therefore, by adding a gradient phase sequence to the first VB generator, the second one is designed to steer the generated beams to a preset direction, which could enable diverse scenarios. The measurement results of both VB generators agree very well with the numerical ones, validating the full control capability of the proposed approach. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement