Study on the Generation of THz Waves in a Vacuum Electronic Device

We proposed a vacuum electronic device based on field emission mechanism for the generation of THz waves in a previous work. The preliminary simulation results showed that an electronic efficiency up to 4% can be achieved with no external magnetic fields applied. However, the interaction mechanism is not clear. In the present work, the interaction mechanisms are studied. The MAGIC code is used to investigate the interactions between the electrons and the THz waves. To understand the interaction mechanism, the cathode has been trimmed to emit electrons. The simulation results show that the efficiency of the case corresponding to the trimmed cathode is higher than that of the original planar cathode. The interaction regions are located among the gaps between the cathode and the anode. The AC electric fields of the THz waves not only velocity-modulate the electron beam but also cause the density modulation of the field emission current. This pre-bunching effect provides the feedback loop as required by an oscillator