1. Center for Microscopy-Microanalysis and Information Processing, University Politehnica Bucharest, Bucharest, Romania
2. Laboratorio de Óptica, Campus de Espinardo (ed. 34), Universidad de Murcia, Murcia, Spain
3. Center for Research and Training in Innovative Techniques of Applied Mathematics in Engineering, University Politehnica of Bucharest, Bucharest, Romania
4. Faculty of Electrical Engineering, University Politehnica of Bucharest, Bucharest, Romania
5. Photonics Laboratory, Physics Unit, Tampere University, Tampere, Finland