1. Center of Materials Technology and Photonics and Electrical Engineering Department; Technological Educational Institute of Crete; Heraklion 71004 Crete Greece
2. Department of Electronic Engineering; Technological Educational Institute of Crete; Chania 73132 Crete Greece
3. Institute of Electronic Structure and Laser; Foundation for Research and Technology-Hellas; Heraklion 71110 Crete Greece