1. The Institute of Scientific and Industrial Research (ISIR),
Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047,
Japan
2. Advanced Technology Research Laboratories,
Panasonic Corporation, 3-4 Hikaridai, Seika-cho, Soraku-gun,
Kyoto 619-0237, Japan
3. Department of Physics and Astronomy, Rutgers
University, Piscataway, New Jersey 00854-8019,
USA