Nizhny Novgorod scientists obtain self-mode-locking regime in microwave gyroresonance source

Scientists from the Faculty of Radiophysics of Lobachevsky University and the Institute of Applied Physics of the Russian Academy of Sciences have conducted experimental studies of the dynamics of a gyroresonant travelling wave tube, which is a powerful electrovacuum source of microwave radiation. They succeeded in obtaining periodic sequences of short pulses formed due to the effect of self-mode-locking with strong external reflections of the output radiation.

The research was conducted as part of the Priority 2030 federal programme of strategic academic leadership. The results were published in the leading international journal in the field of electronic engineering - IEEE Electron Device Letters.

"The generation of high-power short microwave radiation pulses is of significant interest for a number of scientific applications. As an example, we can point out the accelerator applications, where the short pulses may prevent the electric breakdowns and thus increase the limiting values of the acceleration gradients," said Roman Rozental, research leader and Head of the Laboratory of Intense Millimetre Radiation Sources at the UNN Faculty of Radiophysics.

"Since 1996,  the Institute of Applied Physics of the Russian Academy of Sciences has been developing the concept of gyroresonant travelling wave tubes based on the use of a waveguide with a helical corrugated surface. Such devices have a number of unique characteristics, including power, efficiency, operating range and gain bandwidth," said Sergei Samsonov, Head of the Laboratory of Applied Microwave Electronics at the RAS Institute of Applied Physics.

It should be noted that a generator of periodic sequences of subnanosecond pulses based on the effect of passive mode-locking has recently been implemented at the RAS Institute of Applied Physics. The study of the effects of self-mode-locking continues this research. The main advantage of the proposed system is a simpler design, including only a powerful amplifier and a broadband reflector of the output radiation. However, there is also a considerable disadvantage: a significantly longer duration of pulses, which will be the focus of further research.

Modes are the types of oscillations in distributed oscillating systems, such as bulk or optical resonators. The effect of mode locking consists in creating conditions in the system where the generated modes have the same or comparable amplitudes and the phases of the individual modes are related by a certain ratio.