1. Department of Physics, Bilkent University, 06800 Ankara, Turkey.
2. School of Physics and Centre for Research on Adaptive Nanostructures and Nanodevices, Trinity College Dublin, College Green, Dublin 2, Ireland.
3. Department of Photonics, Izmir Institute of Technology, 35430 Izmir, Turkey.
4. Electrical Engineering Department, University of California, Los Angeles, Los Angeles, CA 90095, USA.
5. ICFO–Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels, Barcelona, Spain.
6. Laboratory of Photonics, Tampere University of Technology, 33720 Tampere, Finland.
7. Nanotechnology Research Center–NANOTAM, Bilkent University, 06800 Ankara, Turkey.