1. Experimental Condensed Matter Physics Lab, Department of Physics, University of Cyprus, Nicosia 1678, Cyprus
2. Institute for Electronics, Department of Information Technology and Electrical Engineering, ETH Zurich, CH-8092 Zurich, Switzerland
3. Laboratory of Ultrafast Science, Department of Physics, University of Cyprus, Nicosia 1678, Cyprus
4. Integrated Systems Laboratory, Department of Information Technology and Electrical Engineering, ETH Zurich, CH-8092 Zurich, Switzerland