1. Key Laboratory of Photoelectric Technology of Shaanxi Province, National Center for International Research of Photoelectric Technology & Nano-Functional Materials and Application, Institute of Photonics and Photon-Technology, Northwest University, Xi'an 710069, China
2. College of Electronic Science & Engineering, Jilin University, China
3. Mechanical Engineering Department & Biomedical Engineering Department, University of South Carolina, Columbia, SC 29208, USA