1. Department of Physics, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan
2. Department of Materials and Optoelectronic Science, National Sun Yat-Sen University, Kaohsiung 804, Taiwan
3. Department of Applied Science, Chinese Naval Academy, Kaohsiung 81345, Taiwan and Center for Nanoscience and Nanotechnology, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
4. Department of Photonics, National Sun Yat-Sen University, Kaohsiung, 80424, Taiwan
5. Department of Physics, The Center of Crystal Research, National Sun Yat-Sen University, Kaohsiung 804, Taiwan