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0Microwave-range soliton combs formed based on nonlinear electron-wave interaction
N. Ginzburg, G. Denisov, S. Samsonov, A. Sergeev, V. Vilkov, L. Yurovskiy, I. Zotova*
A.V Gaponov-Grekhov Institute of Applied Physics of the Russian Academy of Sciences, Russia
* zotova@ipfran.ru
Solitons are well-studied objects of optics and appear in many laser systems. Of particular interest is the possibility of periodic formation of so-called dissipative solitons [1,2], which is used, for example, to implement sources of ultrashort light pulses in mode-locked lasers with saturable absorbers [3] or to form ultra-wide frequency combs in Kerr-type microcavities pumped by coherent laser radiation [4,5]. Recently, it was theoretically shown that periodic trains of solitons (hereinafter referred to as soliton combs) can occur in microwave electronics, where they arise due to the nonlinearity of electron-wave interaction. In some cases, the mechanisms of formation of such soliton combs are similar to those known in laser physics. This is due to the fact that, depending on the interaction conditions, the electron beam can act as an active (inverted, emitting), passive (non-inverted, absorbing) or reactive nonlinear medium. At the same time, there are certain specifics associated with the movement of the electron beam, the dispersion of waveguide systems, etc.
The report will present the results of research aimed at the formation of microwave soliton combs. Two main mechanisms are considered. The first type is the modulation of a counterpropagating monochromatic wave and the emergence of solitons of self-induced transparency during cyclotron resonant interaction with magnetized initially rectilinear (passive) electron beams. Of fundamental importance here is the relativistic dependence of the gyrofrequency on the particle energy. The second type is dissipative solitons, similar to those produced in mode-locked lasers and Kerr microcavities. Passive mode locking is implemented in two-section microwave generators consisting of a coupled electron amplifier and a saturable absorber based on cyclotron resonant absorption. The possibility of observing Kerr-like dissipative solitons based on the interaction of monochromatic microwave radiation with a reactive electron beam in a high-Q resonator is also discussed.
Along with the results of theoretical analysis, the results of conducted and planned experiments are presented. We have currently implemented implementing a Ka-band generator of 100 kW/0.4 ns pulses based on a helical-waveguide gyro-TWT mode-locked by a cyclotron-resonance absorber driven by an electron beam [7]. Currently, the same absorber powered by a Ka-band gyro-BWO is planned to be used to observe solitons of self-induced transparency. The feasibility of this mechanism is confirmed on the basis of direct PIC (particle-in-cell) simulations.
This work was supported by the RSF project № 23-12-00291.
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