L.I. Yusupova – Student, 

Department «Radio Engineering, Opto- and Nanoelectronics», Ulyanovsk State Technical University E-mail: lesanusupova@gmail.com

O.V. Ivanov – Dr.Sc.(Phys.-Math.),

Department «Radio Engineering, Opto- and Nanoelectronics», Ulyanovsk State Technical University Ulyanovsk Branch of Kotel’nikov Institute of Radio Engineering and Electronics of RAS E-mail: olegivvit@yandex.ru