[1] Korea Univ, Div Mat Sci & Engn, Seoul 136713, South Korea
[2] Gwangju Inst Sci & Technol, Dept Mat Sci & Engn, Kwangju 500712, South Korea
[3] Georgia Inst Technol, Sch Elect & Comp Engn, Atlanta, GA 30332 USA
[4] Samsung Adv Inst Technol, Photon Program Team, Suwon 440600, South Korea