[1] Natl Chi Nan Univ, Dept Appl Mat & Optoelect Engn, Nantou 54561, Taiwan
[2] Natl Dong Hwa Univ, Dept Phys, Hualien 97401, Taiwan
[3] Natl Dong Hwa Univ, Dept Optoelect Engn, Hualien 97401, Taiwan
[4] Natl Chung Hsing Univ, Dept Elect Engn, Taichung 402, Taiwan
[5] Natl Chung Hsing Univ, Grad Inst Optoelect Engn, Taichung 402, Taiwan