Photonic crystal reflex klystron using field emission cathode

A compact, monochromatic, continuous wave radiation source in the millimeter and submillimeter wave regime was demonstrated. It was shown experimentally that the field pattern of the resonant mode in the photonic crystal cavity is much close to the TM_mno mode compared with the conventional metal cavity. The exclusion of the fundamental resonance mode and some low order resonance modes by using the photonic band gap in the photonic crystal can make the high order TM_mno mode be most dominant. For a proof-of-principle experiment, a 10 GHz reflex klystron adopting the photonic crystal and the field emission cathode was also analytically and numerically designed. It was found out from the particle-in-cell code simulation that the TM₃₃₀-like mode could be successfully activated without any mode competition.