1. Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan.
2. Institute of Photonics Technologies, National Tsing Hua University, Hsinchu, Taiwan.
3. Department of Photonics, National Sun Yat Sen University, Kaohsiung, Taiwan.
4. EECS Department, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
5. Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan.
6. Department of Electrical Engineering and Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, Taiwan.