1. Georgia Tech Lorraine, Georgia Tech-C.N.R.S., UMI2958, 2-3 rue Marconi, 57070 Metz, France
2. School of Electrical and Computer Engineering, Georgia Institute of Technology, 777 Atlantic Drive NW, 30332-0250 Atlanta, USA
3. Université de Lorraine, CentraleSupélec, LMOPS, EA 4423, 2 rue E. Belin, 57070 Metz, France
4. Laboratory for Photonics and Nanostructures, CNRS, Route de Nozay, 91460 Marcoussis, France