Institution: | a Department of Physics, National Changhua University of Education, Changhua 50058, Taiwan b Department of Optics and Photonics, National Central University, No. 300, Jhongda Road, Jhongli City, Taoyuan County 32001, Taiwan c Institute of Precision Engineering, National Chung Hsing University, 250, Kuo Kuang Road, Taichung 402, Taiwan, ROC |