A Novel THz Forward and Backward Wave Two-Mode Band-Edge Oscillator

In this article, a novel two-mode operation concept for the THz oscillator with the folded waveguide is proposed. To demonstrate this concept, a two mode 4π band-edge oscillator has been simulated and fabricated. The simulation predicted that the designed oscillator was capable of delivering maximal output power of over 2 W at 301.7-303 GHz for both forward and backward operation mode. On the other hand, the testing data showed that the first prototype of the two-mode oscillator was able to produce output power over 1 W at about 305.6 GHz (voltage 23.04 kV) and 1.51 W at 308.8 GHz (voltage 24.33 kV), for forward and backward operation mode, respectively, with a 5-7 GHz frequency shift compared to the simulation. The findings demonstrate the correctness of the proposed two-mode concept for developing novel two-mode band-edge oscillators. There exist some inconsistencies between the testing and simulation, which will be discussed in the article. It is believed that the proposed two-mode concept is useful for the exploration of other novel two-mode band-edge oscillators, such as compact, high-power THz radiation sources for potential applications.