1. Optoelectronic Materials and Technologies Engineering Laboratory of Shandong, College of Mathematical and Physical Sciences, Qingdao University of Science and Technology, Qingdao, People’s Republic of China
2. Institut für Festkörperphysik and Zentrum für Nanophotonik, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin, Federal Republic of Germany
3. King Abdul-Aziz University, Kingdom of Saudi Arabia