1. Department of Physics, National Dong Hwa University, Hualien 97401, Taiwan
2. Department of Electrical Engineering, National Dong Hwa University, Hualien 97401, Taiwan
3. Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
4. Department of Physics, Chung Yuan Christian University, Taoyuan 32023, Taiwan
5. Office of Postgraduate Studies, UCSI University, Kuala Lumpur 56000, Malaysia