1. Nanoscale Quantum Photonics Laboratory RIKEN Cluster for Pioneering Research Saitama 351‐0198 Japan
2. Quantum Optoelectronics Research Team RIKEN Center for Advanced Photonics Saitama 351‐0198 Japan
3. Department of Mechanical Engineering The University of Tokyo Tokyo 113‐8656 Japan
4. International Center for Materials Nanoarchitectonics National Institute for Materials Science Ibaraki 305‐0044 Japan
5. Research Center for Functional Materials National Institute for Materials Science Ibaraki 305‐0044 Japan
6. Department of Materials Engineering The University of Tokyo Tokyo 113‐8656 Japan