1. Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan
2. Leibniz Institute of Photonic Technology, Albert-Einstein Straße 9, 07745 Jena, Germany
3. Research Center for Applied Sciences, Academia Sinica, 128 Sec. 2, Academia Road, Nankang District, Taipei 11529, Taiwan
4. Department of Electrophysics, National Chiao Tung University, Hsinchu 30010, Taiwan