1. Korea Research Institute of Standards and Science, Daejeon 305-340, Republic of Korea
2. Department
of Physics, Chonbuk National University, Jeonju 561-756, Republic of Korea
3. School of Materials Science and Engineering, Ulsan National Institute of Science & Technology, Ulsan 689-805, Republic of Korea
4. Korea Institute of Science and Technology, Seoul 136-791, Republic of Korea
5. Korea Photonics Technology Institute, Gwangju 500-779, Republic of Korea