1. Department of Applied Physics, Aalto University School of Science, FI-00076 Aalto, Finland
2. Photophysics Department, The Szewalski Institute, Polish Academy of Sciences, 80-231 Gdansk, Poland
3. Wihuri Physical Laboratory, Department of Physics and
Astronomy, University of Turku, FI-20014 Turku, Finland
4. Materials Research Laboratory, Department
of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland
5. VTT Technical Research Center of Finland, FI-02150 Espoo, Finland