1. National Key Laboratory of Photoelectric Technology and Functional Materials (Culture Base) in Shaanxi Province, National Photoelectric Technology and Functional Materials and Application of Science and Technology International Cooperation
Base, Institute of Photonics and Photon-Technology, Northwest University, Xi’an 710069, P. R. China
2. School of Physics, Northwest University, Xi’an 710069, P. R. China
3. National Laboratory of Solid State Microstructures and School of Physics, Nanjing University, Nanjing 210093, P. R. China