Some physics issues of THz gyrotrons

The gyrotron is a class of powerful radiation source based on the electron cyclotron maser instability. It plays a prominent role in the electromagnetic spectrum by delivering unprecedented power levels in the millimeter and sub-millimeter wavelength regime and hence opening up a wide range of applications. Motivated by still more applications which require moderate to high power terahertz (THz) sources, there have been extensive worldwide research efforts to develop sub-THz and THz gyrotrons, some of which have already broken the THz barrier.