1. Institute of Laser Engineering, Osaka University, 2-6 Yamada-oka, Suita, Osaka 565-0871, Japan
2. Kobe Shinwa Women's University, 7-13-1 Suzurandai Kitamachi, Kita-ku, Kobe 651-1111, Japan
3. Japan Steel Works Ltd., 2-2-1 Hukuura, Kanazawa-ku, Yokohama 236-0004, Japan