1. Department
of Physics, University of Patras, 26504 Patras, Greece
2. Institute
of Chemical Engineering Sciences (ICE-HT), Foundation for Research and Technology-Hellas (FORTH), 26504 Patras, Greece
3. Department
of Engineering Physics, Laser Processing and Plasmonics Laboratories, École Polytechnique de Montréal, Succ.Centre-Ville, Montréal, QC H3C 3A7, Canada