Study of broadband quasi-optical mode converter for THz gyrotron

This paper presents the design of a broadband quasi-optical mode converter for a 330 GHz TE62 mode tunable gyrotron. It consists of a Vlasov launcher and three reflector mirrors. A series of important considerations, including Vlasov launcher of reasonable radius, robust and simple system configuration, are the keys to realize stable and broadband mode converting. The optimized internal converter achieves well compatibility with the gyrotron electron-optical system and generates high-purity Gaussian beam between 320 GHz ~ 340 GHz.