1. Research-Educational Institute of Optics and Biophotonics, Saratov State University, Saratov 410012, Russia
2. Laboratory of Laser Diagnostics of Technical and Living Systems, Institute of Precise Mechanics and Control RAS, Saratov 410028, Russia
3. Optoelectronics and Measurement Techniques Laboratory, P. O. Box 4500, University of Oulu, FIN-90014, Oulu, Finland