1. School of PhysicsCRANN and AMBERTrinity College Dublin Dublin 2 D02 Ireland
2. Theory of Condensed MatterCavendish LaboratoryUniversity of Cambridge J. J. Thomson Avenue Cambridge CB3 0HE UK
3. School of Chemistry and AMBERTrinity College Dublin Dublin 2 D02 Ireland
4. Laboratory of Micro‐Nano Photonic and Optoelectronic Materials and DevicesKey Laboratory of Materials for High‐Power LaserShanghai Institute of Optics and Fine MechanicsChinese Academy of Sciences Shanghai 201800 P. R. China
5. Center of Materials Science and Optoelectronics EngineeringUniversity of Chinese Academy of Sciences Beijing 100049 P. R. China
6. Department of Electrical Engineering and Solid‐State InstituteTechnion‐Israel Institute of Technology Haifa 32000 Israel