1. Key Laboratory for Physical Electronics and Devices of the Ministry of Education & Shaanxi Key Lab of Information Photonic Technique; Xi'an Jiaotong University; Xi'an 710049 China
2. Science Program; Texas A&M University at Qatar; P.O. Box 23874 Doha Qatar
3. Zhou Pei-Yuan Center for Applied Mathematics; Tsinghua University; Beijing 100084 China
4. Department of Electronic and Information Engineering; Shunde Polytechnic; Shunde 528300 China
5. CREOL; College of Optics and Photonics; University of Central Florida; Orlando Florida 32816-2700 USA
6. Department of Physics; University of Arkansas; Fayetteville Arkansas 72701 USA
7. National Laboratory of Solid State Microstructures and School of Physics; Nanjing University; Nanjing 210093 China