1. Department of Physics, Duke University, Durham, North Carolina 27708, USA
2. Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708, USA
3. Department of Mathematics and Physics, North Carolina Central University, Durham, North Carolina 27707, USA
4. Laser Zentrum Hannover e.V., Hollerithallee 8, Hannover 30419 NI, Germany
5. Laseroptik GmbH, Horster Str. 20, Garbsen 30826 NI, Germany
6. Trumpf Laser GmbH & Co. KG, Johann-Maus-Str. 2, Ditzingen 71254 BW, Germany