[1] Nicholas Copernicus Univ, Inst Phys, Ul Grudziadzka 5-7, PL-87100 Torun, Poland
[2] Adam Mickiewicz Univ, Fac Phys, PL-61614 Poznan, Poland
[3] Univ Warsaw, Fac Phys, PL-00681 Warsaw, Poland
[4] Gdansk Univ Technol, Fac Appl Phys & Math, PL-80952 Gdansk, Poland