1. Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE, United Kingdom
2. International Research Centre for Nanophotonics and Metamaterials, ITMO University, Birjevaja line V.O. 14, St. Petersburg 199034, Russia
3. Department of Electrical and Electronic Engineering, Public University of Navarra, Arrosadia, Pamplona, Navarra 31006, Spain
4. Optical and Semiconductor Devices Group, Department of Electrical and Electronic Engineering, Imperial College London, SW7 2BT London, United Kingdom
5. Center for Integrated Nanotechnologies, Sandia National Laboratory, Albuquerque, New Mexico 87185, USA
6. Sandia National Laboratory, Albuquerque, New Mexico 87185, USA
7. St. Petersburg State Polytechnic University, Politekhnicheskaya 29K1, St. Petersburg 194064, Russia