1. Computer,
Electrical and Mathematical Sciences and Engineering (CEMSE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia
2. Institute of Photonics and Optoelectronics & Department of Electrical Engineering, National Taiwan University, Taipei 10617, Taiwan, Republic of China
3. Department
of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR
4. Department
of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan, Republic of China