1. Department of Physics, National Changhua University of Education, Changhua 500207, Taiwan
2. Department of Electronic Engineering, National Changhua University of Education, Changhua 500208, Taiwan
3. Graduate Institute of Photonics, National Changhua University of Education, Changhua 500207, Taiwan
4. Department of Information and Communication Engineering, Chaoyang University of Technology, Taichung 413310, Taiwan
5. Department of Electronic Engineering, Chienkuo Technology University, Changhua 500020, Taiwan