Transmission type dual-frequency vortex beams generator for multiple OAM modes

We design a transmission-type metasurface to generate terahertz dual-frequency orbital angular momentum (OAM) vortex beams with different topological charges (l = 1, l = 2) at frequency of 0.81THz and 1.63THz. By adding a deflection factor, the proposed metasurface produces a OAM vortex beam with a preset tilted direction at two frequencies. By utilizing a complex convolution operation, we can achieve two symmetric tilted beams with different topological charges (l = 1, l = − 1) at two frequencies on the same metasurface. These OAM vortex beams can effectively improve communication system capacity, and have potential applications in terahertz communication.