[1] Mil Univ Technol, Inst Optoelect, PL-01489 Warsaw 49, Poland
[2] Acad Sci Czech Republ, Inst Phys, Prague 18040 8, Czech Republic
[3] Inst Plasma Phys & Laser Microfus, PL-00908 Warsaw, Poland
[4] Kansas State Univ, JR Macdonald Lab, Dept Phys, Manhattan, KS 66506 USA