Third-Harmonic Operating Extended Interaction Oscillator

A promising version of THz extended interaction oscillator (EIO) is developed to operate in high harmonic, which permits a breakthrough in the frequency limits of conventional version supported by fundamental mode. The specific design and mode analysis in the ladder-type RF circuit is carried out to excite the third harmonic on the base of the effective modulation with the fundamental mode. The dispersion characteristic of the RF circuit is analyzed to discuss the feasibility of the operation in the third harmonic. To demonstrate the circuit capability, the beam-wave interaction with respect to the fundamental mode and third harmonic is studied by using 3-D Particle-in-cell simulation technology. The third harmonic radiation from a low-frequency RF circuit is achieved by using this method and the start current still maintain the normal level in the low-frequency RF circuit. This provides a novel method for pushing the development of the THz radiation sources.