Abstract
The gyrotron backward-wave oscillator (gyro-BWO) is a frequency tunable scheme at millimeter/terahertz regime. The continuous frequency tuning can be achieved by varying either the magnetic field or the beam voltage in a non-resonant structure. With a growing interest in terahertz-wave regime, gyro-BWO should be preferably operated with high-order mode due to the power-handling capability. Then the upcoming difficulty would be the terahertz interaction circuit as well as the severe transverse mode competition. © 2009 IEEE.