1. Department of Electrical and Computer Engineering, National University of Singapore, 117576 Singapore
2. Center for Intelligent Sensors and MEMS (CISM), National University of Singapore, 117576 Singapore
3. Department of Micro/Nano Electronics, Shanghai Jiao Tong University, Dong Chuan Road 800, 200240 Shanghai, People's Republic of China
4. Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore
5. Center for Disruptive Photonic Technologies, The Photonics Institute, 50 Nanyang Avenue, Nanyang Technological University, 639798 Singapore
6. Graduate School for Integrative Science and Engineering, National University of Singapore, Singapore