1. Institute of Laser Engineering, Osaka University,Suita, Osaka,Japan,565-0871
2. Nippo Precision Co., Ltd.,Nirasaki, Yamanashi,Japan,407-0175
3. Arizona State University,Tempe,AZ,USA,85287
4. National Institute of Materials Physics,Bucharest-Magurele,Romania,077125
5. University of Fukui,Research Center for Development of Far-Infrared Region,Fukui,Japan,910-8507