1. Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China
2. College of Physics Science and Technology, Guangxi Key Laboratory for the Relativistic Astrophysics, Laboratory of Optoelectronic Materials and Detection Technology, Guangxi University, Nanning 530004, People's Republic of China
3. Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, 1001 Ta Hsueh Road, Hsinchu 300, Taiwan