Competition-free second harmonic mode THz orbital angular momentum gyrotron with dual-mode operation by a perturbed cavity

Abstract

We propose a dual-mode orbital angular momentum (OAM) scheme at 400 GHz that uses a gyrotron. A conventional gyrotron with two modes of operation has a second harmonic resonance that competes with the fundamental mode. We used a perturbed cavity to reduce the fundamental mode competition in a second harmonic gyrotron by allowing higher-order axial mode operation. Based on a simulation using an in-house self-consistent gyrotron code, we demonstrated that the operating dual second harmonic modes TE6,4(+)/TE12,2(+) of the OAM source in the perturbed cavity at around 400 GHz can be excited without competition from the fundamental mode TE4,2(−).