1 Institute of Physics, Nanotechnology and Telecommunications, St. Petersburg State Polytechnic University, 29 Polytechnicheskaya, St. Petersburg, 195251 Russia ; Department of Physics and Technology of Nanostructures, St. Petersburg Academic University, 8/3 Khlopina, St. Petersburg, 194021 Russia.
2 Institute of Physics, Nanotechnology and Telecommunications, St. Petersburg State Polytechnic University, 29 Polytechnicheskaya, St. Petersburg, 195251 Russia ; Institute of Photonics, University of Eastern Finland, Yliopistokatu 7, P.O. Box 111, Joensuu, 80101 Finland.
3 Institute of Physics, Nanotechnology and Telecommunications, St. Petersburg State Polytechnic University, 29 Polytechnicheskaya, St. Petersburg, 195251 Russia ; Ioffe Physical-Technical Institute of RAS, 26 Polytechnicheskaya, St. Petersburg, 194021 Russia.
4 Institute of Physics, Nanotechnology and Telecommunications, St. Petersburg State Polytechnic University, 29 Polytechnicheskaya, St. Petersburg, 195251 Russia.