* Corresponding authors

^a Department of Power Mechanical Engineering, National Tsing Hua University, No. 101, Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan
E-mail: steven.sher@hotmail.com

^b Department of Photonics & Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan
E-mail: hckuo@faculty.nctu.edu.tw

^c Institute of Photonic System, National Chiao Tung University, Tainan 711, Taiwan
E-mail: chienchunglin@faculty.nctu.edu.tw
Fax: +886-6-3032535
Tel: +886-6-3032121#57754

^d Department of Electrical Engineering, Da Yeh University, Changhua 51591, Taiwan