1. Department of Photonics, Advanced
Optoelectronic Technology Center, National Cheng Kung University, Tainan 701, Taiwan
2. Department of Mechanical Engineering, National Cheng Kung University, Tainan 701, Taiwan
3. Department of Physics, ROC Military Academy, Kaohsiung 830, Taiwan
4. National Synchrotron Radiation Research Center, Hsinchu 301, Taiwan