1. Nanophotonics Center, NTT Corporation, 3-1, Morinosato Wakamiya, Atsugi, Kanagawa 243-0198,
Japan
2. NTT Basic Research Laboratories, NTT Corporation, 3-1, Morinosato Wakamiya, Atsugi, Kanagawa 243-0198,
Japan
3. NTT Device Technology Laboratories, NTT Corporation, 3-1, Morinosato Wakamiya, Atsugi, Kanagawa 243-0198,
Japan