M.V. Davidovich – Dr.Sc.(Phys.-Math.), Professor,  Department of Radiotechnique and Electrodynamics, 

Saratov national research state University named after N.G. Chernyshevsky

E-mail: davidovichmv@info.sgu.ru

A.K. Kobets – Post-graduate Student, 

Department of Solid State Physics, Saratov national research state University named after N. G. Chernyshevsky E-mail: cobets.alexander@yandex.ru