1. Department of Applied Physics, Tohoku University, Sendai 980-8579, Japan
2. Department of Engineering and Applied Sciences, Sophia University, Chiyoda, Tokyo 102-8554, Japan
3. Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
4. Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
5. Research Center for Development of Far-Infrared Region, University of Fukui, Fukui 910-8507, Japan
6. Department of Applied Physics, Faculty of Engineering, University of Fukui, Fukui 910-8507, Japan
7. Institute of Physics, Siberian Branch of the Russian Academy of Science, 660036 Krasnoyarsk, Russia