Some recent progresses on electron cyclotron maser research

Over a span of five decades, the electron cyclotron maser (ECM) has undergone a remarkably successful evolution from basic research to a powerful millimeter, sub-millimeter, and THz wave generator called the gyrotron, while continuously being enriched by major advances. Below we discuss the ECM principle and its significance, followed by an overview of recent progresses made in two specific areas: THz gyrotron oscillators and millimeter-wave gyro-TWT amplifiers. Topics of the talk will include selected examples of device performances, ongoing/potential applications, and relevant physics issues.