1. FESTA Laboratories, The Femtosecond Technology Research Association, 5-5 Tokodai, Tsukuba, Ibaraki 300-2635, Japan, Corporate Research Laboratories, Fuji Xerox Co. Ltd., 430 Sakai, Nakaimachi, Kanagawa 259-0157, Japan, and Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba, Ibaraki 305-8568, Japan