1. Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan
2. Department of Photonics, National Sun Yat-sen University, Kaohsiung, Taiwan
3. Department of Computer Science, Boston University, Boston, MA, USA
4. College of Semiconductor and Advanced Technology Research, National Sun Yat-sen University, Kaohsiung, Taiwan
5. Department of Physics, the Center of Crystal Research, and College of Semiconductor and Advanced Technology Research, National Sun Yat-sen University, Kaohsiung, Taiwan