Study of a continuous-wave terahertz radiation source based on a vacuum photocathode diode

The terahertz (THz) technology has various potential applications in imaging, sensing, and communication. However, the scarcity of THz radiation sources remains a fundamental bottleneck constraining the progress of THz technology. In this article, a continuous-wave THz radiation source based on a vacuum photocathode diode is designed, which combines the advantages of semiconductor electronics, vacuum electronics, and optics. To address the limited physical mechanisms and simulation methods, the mechanism of this device is theoretically analyzed, and a simulation methodology based on COMSOL Multiphysics is developed. Simulation results show that the radiated power exceeds 0.12 mW over 0.1-1.3 THz, peaking at 1.27 mW (0.2 THz). Its critical components (miniaturized THz antenna, vacuum photocathode diode) are processed using the micro-electro-mechanical system (MEMS) technology. Measurement results show that the vacuum diode achieved a current density of 142.6 mA/cm² under 450 mW laser excitation. This research provides a systematic design methodology and MEMS fabrication exploration for this novel THz source, laying a solid foundation for its further development and application.