1. FORTH/IESL , N. Plastira 100 , Heraklion 70013 , Greece
2. Optoelectronics and Biomedical Photonics Group, AIPT , Aston University , Birmingham B4 7ET , UK
3. Laser Research Center , Vilnius University , Saulėtelio al. 10 , Vilnius 10223 , Lithuania
4. Lidaris Ltd. , Saulėtekio al. 10 , Vilnius LT-10223 , Lithuania
5. Nanotypos , VEPE Technopoli Thessaloniki, Building C2, Pylea , Thessaloniki 55535 , Greece
6. NCSR Demokritos , Institute of Nanoscience and Nanotechnology , P. Grigoriou 27 & Neapoleos Str. , Ag. Paraskevi 15341 , Greece
7. Physics Department , University of Crete , Heraklion 70013 , Greece
8. Materials Science and Technology Department , University of Crete , Heraklion 70013 , Greece