1. Department of Physics; King's College London; Strand, London WC2R 2LS UK
2. Department of Electronic & Electrical Engineering; UCL; London WC1E 7JE UK
3. ITMO University; St. Petersburg 199034 Russia
4. Institute of Physics; Academy of Sciences of the Czech Republic; 18221 Prague 8 Czech Republic
5. Center for Integrated Nanotechnologies; Sandia National Laboratories; NM 87185 USA
6. Sandia National Laboratories; Albuquerque New Mexico 87185 USA
7. ICMCB; University of Bordeaux; CRNS, UPR 9048, 87 Avenue du Docteur Schweitzer 33608 Pessac France
8. IMS; University of Bordeaux; CNRS, UMR 5218, 351 Cours de la Libération 33405 Talence France