1. Department of Information Engineering, University of Padua, Padua, Italy
2. LIGENTEC SA, Ecublens, Switzerland
3. Department of Microtechnology and Nanoscience, Photonics Laboratory, Chalmers University of Technology, Goteborg, Sweden
4. Photonics Research Group, Ghent University-imec, Ghent, Belgium
5. Department of Information Engineering and the Department of Physics and Astronomy, University of Padua, Padua, Italy