1. RIKEN Center for Advanced Photonics (RAP), RIKEN, 519-1399 Aramaki-Aoba, Sendai, Miyagi 980-0845, Japan
2. Advanced Device Research and Development Center, Ricoh Company, Ltd., 5-10 Aza-Yokara-Kami, Kumanodo Takadate, Natori, Miyagi 981-1241, Japan