[1] Univ Mons, Electromagnetism & Telecom Dept, B-7000 Mons, Belgium
[2] Fdn Res & Technol Hellas FORTH, Inst Elect Struct & Laser IESL, Iraklion 70013, Greece
[3] European Univ Cyprus, EUC Res Ctr, Sch Sci, CY-1516 Nicosia, Cyprus
[4] Lumoscribe Ltd, Photon Res Ctr PRC, CY-8201 Paphos, Cyprus
[5] Czech Acad Sci, Inst Photon & Elect UFE, Chaberska 57,8 Kobylisi, Prague 18200, Czech Republic