1. Department
of Environmental Science and Technology, Graduate School of Science
and Technology, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553, Japan
2. Nagano Prefectural
Institute of Technology, 813-8 Shimonogo, Ueda, Nagano 386-1211, Japan
3. Central
Research Laboratory, Hamamatsu Photonics K.K., 5000 Hirakuchi, Hamamatsu, Shizuoka 434-8601, Japan