1. Research Center for Applied Sciences, Academia Sinica, Taipei, 11529, Taiwan
2. Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 106, Taiwan
3. Department of Material Science and Engineering, National Chiao Tung University, Hsinchu 300, Taiwan
4. Department of Photonics, National Chiao Tung University, HsinChu 300, Taiwan.