[1] Friedrich Alexander Univ, Max Planck Inst Sci Light, Staudtstr 2, D-91058 Erlangen, Germany
[2] Univ Maryland Baltimore Cty, Dept Comp Sci & Elect Engn, Baltimore, MD 21250 USA
[3] Friedrich Alexander Univ, Dept Phys, Staudtstr 2, D-91058 Erlangen, Germany
[4] Chinese Acad Sci, Shanghai Inst Opt & Fine Mech, State Key Lab High Field Laser Phys, Shanghai 201800, Peoples R China