Generators of High-Power Ultrashort Microwave Pulses with a Saturable Absorber in a Feedback Circuit

Abstract

We study theoretically the mechanism of the formation of high-power ultrashort microwave pulses, which is based on the effect of passive mode locking in electron generators, whose feedback circuit includes a nonlinear saturable absorber (amplitude filter). The mechanism under consideration is an analog of the well-known method of generation of ultrashort pulses, which is used widely in laser physics. Nevertheless, realization of this method in electron generators has certain specific features connected with the motion of the active medium (electron flow). It is shown that being applied to vacuum electronics, this method is sufficiently universal, and various types of both relativistic and subrelativistic amplifiers operated in wavelength ranges from the centimeter to submillimeter ones can be used for actualization of ultrashort pulse generators as active elements. In the additional section, which acts as a saturable absorber, one can use either the Kompfner absorption effect, or the effect of cyclotron resonance absorption of radiation by a rectilinear electron beam. It is demonstrated on the basis of numerical simulation that the peak power of ultrashort pulses in electron generators with passive mode locking can exceed the power achieved in the stationary generation regimes significantly and, in some cases, the power of the electron flow.