Owing to the eigenstates of orbital angular momentum (OAM) are infinite and orthogonal to each other, OAM can improve communication capacity infinitely. In this paper, we propose a terahertz vortex beam generator on transmissive metasurfaces. When the y-polarized terahertz wave illuminates vertically to the metasurface along the -z direction, the proposed metasurface generates terahertz vortex beams with topological charges l = ±1, l = ±2 and l = ±3 at the frequency ranging from 0.3 THz to 0.9 THz. We study the far-field radiation, electric field phase, amplitude characteristics, and mode purity with different topological charges. The simulation results are in good agreements with the theoretical predictions.

由于轨道角动量（OAM）的本征态是无限的并且相互正交，OAM可以无限地提高通信容量。在本文中，我们提出了一种在透射超表面上的太赫兹涡旋光束发生器。当y极化太赫兹波沿 - z方向垂直照射超表面时，所提出的超表面会产生具有拓扑电荷l  = ±1、l  = ±2 和l 的太赫兹涡旋光束 = ±3，频率范围为 0.3 THz 至 0.9 THz。我们研究了不同拓扑电荷的远场辐射、电场相位、振幅特性和模式纯度。模拟结果与理论预测非常吻合。