Chung Hyeongju, Kim Daeik, Sawant Ashwini, Lee Ingeun, Choi Eunmi, Lee Jongwon
School of Electrical and Computer Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Korea.
Department of Physics, Ulsan National Institute of Science and Technology, Ulsan, 44919, Korea.
Sci Rep. 2020 May 19;10(1):8289. doi: 10.1038/s41598-020-65230-7.
Vortex beams carrying orbital angular momentum (OAM) have attracted considerable attention for the development of high-capacity wireless communication systems due to their infinite sets of orthogonal modes. However, the practical applications of Laguerre-Gaussian type vortex beams are limited due to the fact that the divergence angle increases as the order of the OAM mode increases. In this work, we present metasurfaces that generate vortex beams carrying OAM modes with reduced divergence angles in the E-band frequency range. The metasurfaces were designed using eight different meta-atom phase elements, including a spiral phase distribution for OAM modes l = 1 and 2, a phase gradient array to avoid interference with the source beam, and a lens pattern array to reduce the divergence angle. Through simulation and experimental measurement, it was confirmed that the divergence angle of the vortex beam generated by the metasurface with the lens pattern was reduced from 13° to 9° and 14° to 11° for OAM modes l = 1 and 2, respectively, in comparison with the metasurface without the lens pattern. Our results provide new design methods for various applications based on OAM multiplexing especially in high frequency E-band range.
由于具有无限组正交模式，携带轨道角动量（OAM）的涡旋光束在高容量无线通信系统的发展中引起了相当大的关注。然而，拉盖尔 - 高斯型涡旋光束的实际应用受到限制，因为发散角会随着OAM模式的阶数增加而增大。在这项工作中，我们展示了一种超表面，它在E波段频率范围内产生携带OAM模式且发散角减小的涡旋光束。该超表面是使用八种不同的超原子相位元件设计的，包括用于OAM模式l = 1和2的螺旋相位分布、一个避免与源光束干涉的相位梯度阵列以及一个用于减小发散角的透镜图案阵列。通过模拟和实验测量证实，与没有透镜图案的超表面相比，带有透镜图案的超表面所产生的涡旋光束对于OAM模式l = 1和2的发散角分别从13°减小到9°以及从14°减小到11°。我们的结果为基于OAM复用的各种应用，特别是在高频E波段范围内，提供了新的设计方法。
