[1] Univ San Diego, Dept Phys & Biophys, San Diego, CA 92110 USA
[2] Washington State Univ, Dept Phys & Astron, Pullman, WA 99164 USA
[3] Missouri Univ Sci & Technol, Dept Phys, Rolla, MO 65409 USA
[4] Univ Massachusetts, Dept Math & Stat, Amherst, MA 01003 USA
[5] Univ Hamburg, Ctr Opt Quantum Technol, Dept Phys, Luruper Chaussee 149, D-22761 Hamburg, Germany
[6] Univ Hamburg, Hamburg Ctr Ultrafast Imaging, Luruper Chaussee 149, D-22761 Hamburg, Germany