1. Department of Physics and Center for Optoelectronics and Photonics Paderborn (CeOPP), Paderborn University, Warburger Strasse 100, Paderborn 33098, Germany
2. International Science and Technology Innovation Cooperation Base for Advanced Display Technologies of Hunan Province, School of Physics and Electronics, Hunan University, Changsha 410082, China
3. Wyant College of Optical Sciences, University of Arizona, Tucson, AZ 85721, USA