[1] Natl Cent Univ, Dept Opt & Photon, Jhongli 320, Taiwan
[2] Natl Tsinghua Univ, Brain Res Ctr, Hsinchu 30013, Taiwan
[3] Friedrich Schiller Univ Jena, Inst Appl Phys, Abbe Ctr Photon, Max Wien Pl 1, D-07743 Jena, Germany
[4] Natl Tsinghua Univ, Inst Photon Technol, Dept Elect Engn, Hsinchu 30013, Taiwan