1. Graduate School of Information Science and Technology, Hokkaido University, Kita 14, Nishi 9, Kita-ku, Sapporo 060-0814, Japan
2. Kitami Institute of Technology, 165 Koen-cho, Kitami, Hokkaido 090-8507, Japan
3. Suzhou QiangMing Optoelectronics, Co. Ltd., Jiangsu, China