1. Center for Subwavelength Optics and Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea
2. Photonic Systems Laboratory, School of EECS, Seoul National University, Seoul 151-744, Korea
3. Metal-Insulator Transition Lab., ETRI, Daejeon 305-350, Korea
4. Department of Physics, Korea University, Seoul 136-701, Korea
5. Division of Energy Systems Research, Ajou University, Suwon 443-749, Korea