1. Department of Physics, Faculty of Electrical Engineering and Communication, Brno University of Technology, Technická 2848/8, 61600 Brno, Czech Republic Brno, Czech Republic
2. The Directorate of Research, Development and Innovation Management (DMCDI), The Technical University of Cluj-Napoca, 15 C-tin Daicoviciu St., Cluj-Napoca, 400020 Cluj-Napoca, Romania