1. NTT Corporation,NTT Basic Research Laboratories,Atsugi-shi, Kanagawa,Japan,243-0198
2. NTT Corporation,NTT Device Technology Laboratories,Atsugi-shi, Kanagawa,Japan,243-0198
3. College of Engineering, Nihon University,Department of Electrical and Electronic Engineering,Koriyama-shi, Fukushima,Japan,963-8642
4. University of Otago,The Dodd-Walls Centre for Photonic and Quantum Technologies,Department of Physics,Dunedin,New Zealand,9016