1. Department of Information Engineering, University of Padua, Padua, Italy
2. Photonics Research Group IMEC, Ghent University, Gent, Belgium
3. Department of Microtechnology and Nanoscience, Photonics Laboratory, Chalmers University of Technology, Günther, Sweden
4. IMEC, Leuven, Belgium
5. Department of Information Engineering, Department of Physics and Astronomy, University of Padua, Padua, Italy