1. Institute
of Electromagnetic Fields, ETH Zurich, Zurich 8092, Switzerland
2. Institute
of Photonics and Quantum Electronics (IPQ) and Institute of Microstructure
Technology (IMT), Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany
3. Department
of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States