1. Department of Optics and Photonics, National Central University, Taoyuan, Taiwan
2. Department of Applied Physics, State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Chongqing, China
3. Department of Applied Materials and Optoelectronic Engineering, National Chi Nan University, Nantou, Taiwan
4. Department of Materials Science and Engineering, City University of Hong Kong, Kowloon, Hong Kong, SAR, China
5. School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA, USA