1. Department of Electrical and Computer Engineering, The Ohio State University, 205 Dreese Lab, 2015 Neil Avenue, Columbus, Ohio 43210, United States
2. Department of Physics, Ohio State University, 191 W. Woodruff Avenue, Columbus, Ohio 43210, United States
3. Department of Physics, Cornell University, 171 Clark Hall, Ithaca, New York 14850, United States
4. Institut für Experimentelle Physik II, Universität Leipzig, Linnéstrasse 5, 04103 Leipzig, Germany