1. Dept. Quantum Systems , Leibniz Institute of Photonic Technology , Albert-Einstein-Str. 9, D-07745 Jena , Germany
2. Advanced Electromagnetics Group, Technische Universitaet Ilmenau , Helmholtzplatz 2, D-98684 Ilmenau , Germany
3. Institute of Geophysics, University of Münster , Corrensstr. 24, D-48149 Münster , Germany
4. Supracon AG , An der Lehmgrube 11, D-07751 Jena , Germany
5. DIAS Geophysical Ltd. , 2131 Airport Drive, S7L 7E1 , Saskatoon , SK , Canada