1. Key Laboratory for Physical Electronics and Devices of the Ministry of Education and Shaanxi Key Lab of Information Photonic TechniqueXi'an Jiaotong University Xi'an 710049 China
2. Department of PhysicsCity University of Hong Kong Kowloon 999077 Hong Kong SAR China
3. Department of Electrical EngineeringSukkur IBA University Sindh 65200 Pakistan