1. School of electrical Engineering and Computer Science Gwangju Institute of Science and Technology Gwangju 61005 Republic of Korea
2. Next Generation LED Research Center Korea Photonics Technology Institute Gwangju 61007 Republic of Korea
3. Photonics Laboratory King Abdullah University of Science and Technology Thuwal 23955 Saudi Arabia
4. School of Materials Science and Engineering Gwangju Institute of Science and Technology Gwangju 61005 Republic of Korea