1. Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
2. Center for Advanced High Magnetic Field Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
3. Institute of Laser Engineering, Osaka University, Suita, Osaka 565-0871, Japan
4. Department of Applied Physics, Stanford University, CA 94305, U.S.A.