1. School of Electronic and Optical Engineering and College of Microelectronics, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
2. Photonic Research Centre, University of Malaya, 50603 Kuala Lumpur, Malaysia
3. Division of Advanced Materials Engineering, Jeonbuk National University, Jeonju 54896, South Korea
4. Hydrogen and Fuel Cell Center, Jeonbuk National University, Jeonju 54896, South Korea
5. Photonics Laboratory, King Abdullah University of Science and Technology, Thuwal 23955, Saudi Arabia
6. Korea Advanced Nano Fab Center, Suwon 16229, South Korea