1. Department of Physics, Faculty of Electrical Engineering and Communication, Brno University of Technology, Technická 2848/8, 61600 Brno, Czech Republic
2. CEITEC BUT—Brno University of Technology, Purkynova 656/123, 61200 Brno, Czech Republic
3. Institute of Scientific Instruments of the Czech Academy of Sciences, Královopolská 147, 61264 Brno, Czech Republic