1. Division of Applied Physics, Faculty of Pure and Applied Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan
2. Devices & Materials Labs Fujitsu Laboratories Ltd., Atsugi, Kanagawa 243-0197, Japan
3. ICE Cube Center, Tokyo Institute of Technology, Yokohama 226-8503, Japan
4. Disco Corporation, Ota, Tokyo 143-8580, Japan
5. Research Institute of Instrumentation Frontier, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan