1. Optics Laboratory, School of Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland;
2. Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratories, Richland, Washington 99352, USA
3. Institute of Bioengineering, School of Engineering, EPFL, CH-1015, Lausanne, Switzerland
4. Laboratory for Fundamental BioPhotonics, Institute of Bioengineering, School of Engineering, EPFL, CH-1015, Lausanne, Switzerland
5. Institute of Chemical Sciences and Engineering, EPFL, CH-1015 Lausanne, Switzerland