[1] INESC Porto, P-4169007 Oporto, Portugal
[2] Shahid Beheshti Univ, Laser & Plasma Res Inst, Tehran 1983963113, Iran
[3] Univ Madeira, Dept Matemat & Engn, P-9000390 Funchal, Portugal
[4] Univ Porto, Fac Ciencias, Dept Fis, P-4169007 Oporto, Portugal
[5] Univ N Carolina, Dept Phys, Charlotte, NC 28223 USA
[6] Inst Photon Technol IPHT, D-07745 Jena, Germany