1. Kavli Institute
of Nanoscience, Delft University of Technology, 2600 GA Delft, The Netherlands
2. Instytut Fizyki, UMK, Grudziądzka 5, Toruń 87-100, Poland
3. Laboratoire
de Photonique et de Nanostructures, CNRS, route de Nozay, 91460 Marcoussis, France
4. Department of Photonics Engineering, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
5. Department
of Applied Physics, KTH Royal Institute of Technology, SE-100 44, Stockholm, Sweden