1. Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan
2. Diamond Material Team, Advanced Power Electronics Research Center, National Institute of Advanced Industrial Science and Technology, 1-8-31 Midorigaoka, Ikeda, Osaka 563-0026, Japan
3. Joining and Welding Research Institute, Osaka University, 11-1, Mihogaoka, Ibaraki, Osaka 567-0047, Japan
4. Institute for Laser Technology, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan
5. Graduate School for the Creation of New Photon Industries, 1955-1 Kurematsu, Nishiku, Hamamatsu, Shizuoka 141-1201, Japan