1. Faculty of Electrical Engineering and Electronics Kyoto Institute of Technology Hashikamicho, Sakyo‐ku, Kyoto‐shi Kyoto 606‐8585 Japan
2. New Industry Creation Hatchery Center Tohoku University Aza‐Aoba, Aramaki, Aoba‐ku Sendai Miyagi 980‐8579 Japan
3. Institute for Materials Research Tohoku University Katahira, Aoba‐ku Sendai Miyagi 980‐8577 Japan
4. Institute of Laser Engineering Osaka University Yamadaoka, Suita Osaka 565‐0871 Japan
5. Institute for Integrated Radiation and Nuclear Science Kyoto University Asashiro Nishi, Kumatori‐cho, Sennan‐gun Osaka 590‐0494 Japan