1. Nanostructured Materials and Devices Laboratory, School of Engineering, University of Cyprus,
P.O. Box 20537, Nicosia 1678, Cyprus
2. Laboratory of Ultrafast Science, Department of Physics, University of Cyprus, P.O. Box 20537, Nicosia 1678, Cyprus
3. Department of Physics, Aristotle University of Thessaloniki, Thessaloniki GR-54124, Greece