1. Research Center for Integrated Quantum Electronics, Hokkaido University, Kita-13 Nishi-8, Kita-ku, 060-8628 Sapporo, Japan
2. Institute of Physics-CND, Silesian University of Technology, Konarskiego 22B, 44-100 Gliwice, Poland
3. Institute of Electrical Engineering, Slovak Academy of Sciences, Dubravska cesta 9, 841 04 Bratislava, Slovak Republic