1. Department of Physics, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand
2. Research and Educational Center for Natural Sciences, Keio University, Yokohama 223-8521, Japan
3. Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577, Japan
4. Physics Department, Ehime University, Matsuyama 790-8577, Japan