Vortex beams carry orbital angular momentum (OAM), which can increase channel capacity in communication systems. In 2019, the International Telecommunication Union designated the terahertz band as the sixth generation wireless communication carrier, so it is very meaningful to study the OAM of terahertz waves. In this letter, we demonstrated a reflective metasurface terahertz vortex beam generator with a wide operating bandwidth (1.6 ∼ 2.4 THz), which consists of a gold metasurface array and a gold ground plane separated by a polyimide layer. Under illumination of circularly-polarized waves, the proposed metasurface produces vortex beams with topological charges of l = 1, l =2, and l = 3 with the mode purity larger than 0.6. Simulation results are in good agreement with the theoretical predictions. Our approach provides a new idea for the design of terahertz vortex wave generators.

涡旋光束携带轨道角动量 (OAM)，可增加通信系统中的信道容量。2019年，国际电信联盟将太赫兹频段指定为第六代无线通信载体，因此研究太赫兹波的OAM是非常有意义的。在这封信中，我们展示了一种具有宽工作带宽（1.6 ∼ 2.4 THz）的反射超表面太赫兹涡旋光束发生器，它由金超表面阵列和由聚酰亚胺层分隔的金接地平面组成。在圆极化波的照射下，所提出的超表面会产生具有l = 1、l = 2 和l拓扑电荷的涡旋光束= 3 模式纯度大于 0.6。模拟结果与理论预测非常吻合。我们的方法为太赫兹涡旋波发生器的设计提供了一种新思路。