1. Korea Photonics Technology Institute, Gwangju 61007, Republic of Korea
2. Microsystems Engineering, NanoPower Research Laboratories, Department of Electrical and Microelectronic Engineering, Rochester Institute of Technology, Rochester, New York 14623, United States
3. Department of Physics, Yeungnam University, Gyeongsan 38541, Republic of Korea
4. Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78712, United States