1. Laser Tech Research Center; Korea Photonics Technology Institute; Gwangju 500-779 South Korea
2. Department of Electronics and Computer Engineering; Chonnam National University; Gwangju 500-757 South Korea
3. Department of Physics; Yeungnam University; Gyeongsan 712-749 South Korea
4. Sensor System Research Center; Korea Institute of Science and Technology (KIST); Seoul 136-791 South Korea
5. Department of Materials Science and Engineering, and Optoelectronics Convergence Research Center; Chonnam National University; Gwangju 500-757 South Korea