1. Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 04001 Kosice, Slovakia
2. Faculty of Physics, Adam Mickiewicz University, Uniwersytetu Poznańskiego 2, 61-614 Poznań, Poland
3. Department of Physics, Faculty of Electrical Engineering and Informatics, Technical University of Kosice, Park Komenskeho 2, 04200 Kosice, Slovakia