1. Regional Centre of Advanced Technologies and Materials, Joint Laboratory of Optics and Departments of Experimental Physics and Physical Chemistry, Faculty of Science, Palacky University, 17 listopadu 1192/12, 771 46 Olomouc, Czech Republic
2. Department of Materials Science and Engineering, University of Erlangen-Nuremberg, Martensstrasse 7, D-91058 Erlangen, Germany
3. Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 14800 Prague, Czech Republic