A Review of Terahertz Traveling Wave Tubes

The terahertz traveling wave tube (TWT), a critical vacuum electronic device, exhibits advantages including wide bandwidth, high power, and superior efficiency. Its applications span high-resolution imaging, high-speed communication, and electronic countermeasures, among others. The operational principle relies on the continuous energy transfer from the electron beam to the electromagnetic wave via interaction within the slow wave structure (SWS), thereby amplifying the signal. The main structure of terahertz TWT is SWS, such as helix, coupling cavity, staggered double vane, folded waveguide (FW), sine waveguide and photonic crystal. Extensive research has been conducted on terahertz TWTs. This review systematically analyzes the characteristics of terahertz TWTs with various SWSs. Additionally, it highlights advancements in achieving high power and wide bandwidth over the past decade. Then several fabrication processes and applications of terahertz TWTs are also described. These insights provide a comprehensive foundation for advancing theoretical and experimental research on terahertz TWTs, thereby accelerating their practical deployment in terahertz technologies.