1 Division of Micro and Nanosystems, KTH Royal Institute of Technology, 11428 Stockholm, Sweden
2 École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
3 Tyndall National Institute, Lee Maltings Complex Dyke Parade, T12 R5CP Cork, Ireland
4 imec vzw. 3DSIP Department, Si Photonics Group, Kapeldreef 75, 3001 Leuven, Belgium
5 Department of Information Technology, Photonics Research Group, Ghent University - IMEC, 9052 Gent, Belgium
6 e-mail: gylfason@kth.se
7 e-mail: frank@kth.se