1. Institute of Materials Science and Applied Research, Vilnius University, Saulėtekio al. 9, Building III, 10222 Vilnius, Lithuania
2. Institute of Solid State Physics, University of Latvia, Kengaraga iela 8, Riga, 10363, Latvia
3. Graduate Institute of Electro-Optical Engineering and Department of Electrical Engineering, National Taiwan University, 1 Roosevelt Road, Sec. 4, Taipei, Taiwan, R.O.C