[1] Palacky Univ, Fac Sci, Dept Opt, Olomouc 77146, Czech Republic
[2] Univ Paderborn, Dept Phys, D-33098 Paderborn, Germany
[3] Univ Paderborn, CeOPP, D-33098 Paderborn, Germany
[4] Univ Aarhus, Dept Phys & Astron, DK-8000 Aarhus C, Denmark
[5] Univ Massachusetts, Dept Phys, Boston, MA 02125 USA
[6] Los Alamos Natl Lab, Div Theoret, Los Alamos, NM 87545 USA
[7] Los Alamos Natl Lab, Ctr Nonlinear Studies, Los Alamos, NM 87545 USA