Affiliation: | 1. Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE (UK);2. Cambridge Display Technology Ltd., Cambourne Business Park, Cambridgeshire CB23 6DW (UK);3. Current address: National Physical Laboratory (NPL), Hampton Road, Teddington TW11 0LW, UK;4. Current address: Department of Physics, Imperial College London, London SW7 2BW, UK |