1. Photonics Devices and System Group , Singapore University of Technology and Design , 8 Somapah Rd , Singapore 487372 , Singapore
2. Microphotonics Center , Massachusetts Institute of Technology , 77 Massachusetts Avenue , Cambridge , MA 02139 , USA
3. Materials Research Laboratory , Massachusetts Institute of Technology , 77 Massachusetts Avenue , Cambridge , MA 02139 , USA
4. Department of Materials Science and Engineering , Massachusetts Institute of Technology , 77 Massachusetts Avenue , Cambridge , MA 02139 , USA
5. Institute of Microelectronics , A*STAR, 2 Fusionopolis Way , #08-02, Innovis Tower , Singapore 138634 , Singapore