Metasurfaces have been successfully employed for realization of orbital angular momentum (OAM) waves, however, current available vortex beam generators suffer from low efficiency and limited bandwidth. In this study, we propose a transparent geometric metasurface composed of InSb cylindroid to generate vortex beams in terahertz region. The operating frequency can achieve broadband coverage from 1.8 THz to 4.5 THz, with a fractional bandwidth of 85.7%, by changing the temperature of the InSb cylindroid from 220K to 340K. Based on geometric phase principle, the full 2π phase shift can be obtained at the operating frequency by rotating the cylindroid. Vortex beam generators with topological charges of +1 and −2 are designed over a broadband range by employing the InSb cylindroid with different temperature. The results indicate that the generated vortex beams have high mode purity at different frequencies. The proposed vortex beam generators can reconstruct the operating frequency by directly changing the external temperature without altering the size of device, which show tremendous potential in wireless communication system.

超表面已成功用于实现轨道角动量 (OAM) 波，但是，当前可用的涡流束发生器效率低且带宽有限。在这项研究中，我们提出了一种由 InSb 圆柱体组成的透明几何超表面，以在太赫兹区域产生涡旋光束。通过将 InSb 圆柱体的温度从 220K 改变到 340K，工作频率可以实现从 1.8 THz 到 4.5 THz 的宽带覆盖，分数带宽为 85.7%。根据几何相位原理，通过旋转圆柱体可以在工作频率下获得完整的 2π 相移。通过采用具有不同温度的 InSb 圆柱体，在宽带范围内设计了具有 +1 和 -2 拓扑电荷的涡流束发生器。结果表明，产生的涡旋光束在不同频率下具有高模式纯度。所提出的涡流发生器可以通过直接改变外部温度而不改变设备尺寸来重建工作频率，这在无线通信系统中显示出巨大的潜力。