1. State Key Laboratory on Tunable Laser Technology, Ministry of Industry and Information Technology Key Lab of Micro-Nano Optoelectronic Information System, School of Science, Harbin Institute of Technology, Shenzhen 518055, China.
2. Department of Engineering and System Science, National Tsing Hua University, Hsinchu 30013, Taiwan.
3. Quantum Solid-State Physics, Department of Physics and Astronomy, KU Leuven, BE-3001 Leuven, Belgium.
4. Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, I-20125 Milano, Italy.