1. Institute of Atomic
and Molecular
Sciences, Academia Sinica, Taipei 10617,
Taiwan
2. Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
3. Department of Electronic Engineering, Chang Gung University, Tao-Yuan 333, Taiwan
4. School of Materials Science
and Engineering, Nanyang Technological University, Singapore
5. Department
of Electrical Engineering
and Computer Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
6. Department
of Photonics, National Chiao Tung University, HsinChu 300, Taiwan