High-Order Vortex Smith-Purcell Radiation via Bragg Law in Multi-Period System

Vortex beams propagate with inherent orbital angular momentum, which can be harnessed for terahertz manipulation, measurement, and communications. Nonetheless, achieving the high-purity generation of high-order topological charges poses a persistent challenge in terms of tunability and operation bandwidth. To overcome these limitations, this paper presents a theoretical and experimental demonstration of a methodology for generating high-order topological charges in emitted vortex Smith-Purcell radiation based on the Bragg law in multi-period systems. The proposed approach offers an alternative means to manipulate vortex free-electron radiation for multi-channel applications, enabling the chiral THz spectroscopy and emissions.