V.E. Ustimchik - Ph.D. (Phys.-Math.), Junior Research Scientist, Kotelnikov IRE RAS (Moscow). E-mail: ustimchikv@gmail.com Yu.K. Chamorovskii - Ph.D. (Phys.-Math.), Leading Research Scientist, Kotelnikov IRE RAS (Moscow) V.N. Filippov - Ph.D. (Phys.-Math.), Research Scientist, Optoelectronic Research Center, Tampere University of Technology (Finland) K.M. Golant - Dr.Sc. (Phys.-Math.), Senior Research Scientist, Kotelnikov IRE RAS (Moscow) S.A. Nikitov - Dr.Sc. (Phys.-Math.), Director, Head of Laboratory, Kotelnikov IRE RAS (Moscow)