1. Department of Photonics and Optical Information Technology, ITMO University, 49 Kronverksky Pr., St. Petersburg 197101, Russia
2. Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoi Prospect V.O. 31, St. Petersburg 199004, Russia
3. Faculty of Physics, St. Petersburg State University, Ulyanovskaya Street 3, Petrodvorets, St. Petersburg 198504, Russia