1. School of Physics, Aristotle University of Thessaloniki, GR-54124, Thessaloniki, Greece
2. Helmholtz-Zentrum Dresden-Rossendorf, PO Box 01328, Dresden, Germany
3. Laboratory of Ultrafast Science, University of Cyprus, Nicosia, PO Box 20537, Nicosia, 1678, Cyprus
4. Nanostructured Materials and Devices Laboratory, School of Engineering, University of Cyprus, PO Box 20537, Nicosia, 1678, Cyprus