1. St. Petersburg
State University, 7/9 Universitetskaya
nab., St. Petersburg 199034, Russia
2. St. Petersburg
National Research University of Information Technologies, Mechanics
and Optics, Kronverkskiy pr. 49, St. Petersburg 197101, Russia
3. Laboratory
of Physics, Lappeenranta University of Technology, Box 20, 53851 Lappeenranta, Finland