title: Observation of dynamic interactions between fundamental and second-harmonic modes in a high-power sub-terahertz gyrotron operating in regimes of soft and hard self-excitation.
abstract: Dynamic mode interaction between fundamental and second-harmonic modes has been observed in high-power sub-terahertz gyrotrons [T. Notake et al., Phys. Rev. Lett. 103, 225002 (2009); T. Saito et al. Phys. Plasmas 19, 063106 (2012)]. Interaction takes place between a parasitic fundamental or first-harmonic (FH) mode and an operating second-harmonic (SH) mode, as well as among SH modes. In particular, nonlinear excitation of the parasitic FH mode in the hard self-excitation regime with assistance of a SH mode in the soft self-excitation regime was clearly observed. Moreover, both cases of stable two-mode oscillation and oscillation of the FH mode only were observed. These observations and theoretical analyses of the dynamic behavior of the mode interaction verify the nonlinear hard self-excitation of the FH mode.
authors.affiliation: Recearch Center for Development of Far-Infrared Region, University of Fukui, 3-9-1 Bunkyo, Fukui, Japan.
authors.forename: Teruo
authors.initials: T
authors.lastname: Saito
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Tatematsu
authors.forename: Yuusuke
authors.initials: Y
authors.lastname: Yamaguchi
authors.forename: Shinji
authors.initials: S
authors.lastname: Ikeuchi
authors.forename: Shinya
authors.initials: S
authors.lastname: Ogasawara
authors.forename: Naoki
authors.initials: N
authors.lastname: Yamada
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Ikeda
authors.forename: Isamu
authors.initials: I
authors.lastname: Ogawa
authors.forename: Toshitaka
authors.initials: T
authors.lastname: Idehara