1. Department
of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States
2. Optical
Materials Engineering Laboratory, ETH Zürich, 8092 Zürich, Switzerland
3. Department
of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States
4. Photonics
Laboratory, ETH Zürich, 8093 Zürich, Switzerland