1. Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei 10617, Taiwan
2. Department of Physics, National Taiwan University, Taipei 10617, Taiwan
3. Department of Photonics, National Cheng Kung University, Tainan 70101, Taiwan
4. Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 70101, Taiwan