1. Department of Electronics and Computer Engineering, Democritus University of Thrace, Xanthi 67100, Greece
2. Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas, P.O. Box 1385, Heraklion, Crete 711 10, Greece
3. Department of Chemistry, University of Crete, Heraklion, Crete 700 13, Greece