1. Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, Higashi 1-1-1, Tsukuba, Ibaraki 305-8565, Japan, and Technical Research Laboratory, Kansai Research Center, Nippon Sheet Glass Co., Ltd., 1, Kaidoshita, Konoike, Itami, Hyogo 664-8520, Japan