Frequency-multiplexed terahertz multiple vortex beam generation

We propose a simple method to generate a frequency-multiplexed terahertz multiple vortex beam using a spiral phase plate and a metallic mask. Using a broadband terahertz source, we experimentally demonstrate the conversion of a terahertz Gaussian beam into a frequency-multiplexed single or multiple vortex beam with topological charges ranging from 1 to 3, which is supported by simulations. This multifunctional device opens new possibilities for high-speed THz communication, information processing, and high-efficiency terahertz wavefront manipulation devices.