1. ICFO-Institut de Ciencies Fotoniques, The Institute of Photonic Sciences, Castelldefels, Barcelona 08860, Spain
2. Institute of Materials Science of Barcelona ICMAB-CSIC Campus UAB, Bellaterra 08193, Spain
3. Corning Research and Development Corporation, Sullivan Park, Corning, New York 14831, United States
4. ICREA-Institució Catalana de Recerca i Estudis Avançats, Passeig Lluís Companys, 23, Barcelona 08010, Spain