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