1. Max Planck Institute for the Science of Light, D-91058 Erlangen, Germany
2. Department of Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, D-91058 Erlangen, Germany
3. Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-Universität Erlangen-Nürnberg,, D-91052 Erlangen, Germany