1. Photonic Materials Unit, National Institute for Materials Science, Tsukuba 305-0044, Japan
2. Doctoral Program in Materials Science and Engineering, Tsukuba University, Tsukuba 305-8573, Japan
3. Synchrotron X-ray Station at SPring-8, National Institute for Materials Science, Hyogo 679-5148, Japan
4. State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, People's Republic of China
5. Wide Bandgap Material Group, National Institute for Materials Science, Tsukuba 305-0044, Japan
6. ICYS-MANA, National Institute for Materials Science, Tsukuba 305-0044, Japan
7. JST-ALCA, The Japan Science and Technology Agency, Tokyo 102-0076, Japan