1. Department of Engineering Science, National Cheng Kung University, Tainan 70101, Taiwan e-mail:
2. Department of Computer and Communication, Shu-Te University, Kaohsiung 82445, Taiwan e-mail:
3. Materials and Electro-Optic Research Division, National Chung-Shan Institute of Science and Technology, Taoyuan 32546, Taiwan e-mail: