1. Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577, Japan
2. Institute of Ultra High Frequency Semiconductor Electronics of RAS, Moscow 117105, Russia
3. Department of Computer Science and Engineering, University of Aizu, Aizu-Wakamatsu 965-8580, Japan
4. Center for Photonics and Two-Dimensional Materials, Moscow Institute of Physics and Technology, Dolgoprudny 141700, Russia
5. Department of Electrical Engineering, University at Buffalo, SUNY, Buffalo, New York 1460-192, USA
6. Department of Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA