1. National Institute of Materials Physics, Laboratory of Optical Processes in Nanostructured Materials, 105 bis Atomistilor Street, P.O. Box MG-7, 077125 Bucharest-Magurele, Romania
2. Institut des Matériaux Jean Rouxel, 2 rue de la Houssinière, B.P. 32229, 44322 Nantes, France