1. Department of Physics, Graduate School of Science, Kobe University, Kobe 657-8501
2. Department of Electrical and Electronics Engineering, Muroran Institute of Technology, Muroran 050-8585
3. Faculty of Integrated Arts and Sciencies, Tokushima University, Tokushima 770-8502
4. Graduate School of Science, Tokyo Metropolitan University, Hachioji 192-0397