1. Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering; National Taiwan University; Taipei 10617, Taiwan Republic of China
2. Department of Photonics Engineering; Yuan Ze University; Chungli, Taoyuan 32003 Taiwan Republic of China
3. Department of Electro-Optical Engineering; National United University; Taiwan Republic of China
4. Nichem Fine Technology Co. Ltd.; Hsinchu County 30267 Taiwan Republic of China