1. University of Colorado, Department of Physics, Boulder, Colorado 80309, USA
2. National Institute of Standards and Technology, Boulder, Colorado 80305, USA
3. LNE-SYRTE, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, 75014 Paris, France
4. Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG, United Kingdom
5. FEMTO-ST, CNRS, 26 Chemin de l‘Epitaphe, 25030 Besançon, France