1. Key Laboratory of In-Fiber Integrated Optics, Ministry of Education, Harbin Engineering University, Harbin 150001, P. R. China
2. Key Laboratory of Photonic Materials and Device Physics for Oceanic Applications, Ministry of Industry and Information Technology of China, Harbin Engineering University, Harbin 150001, P. R. China
3. Leibniz Institute of Surface Engineering (IOM), Permoserstr. 15, Leipzig 04318, Germany
4. Laboratory of Infrared Materials and Devices, The Research Institute of Advanced Technologies, Ningbo University, Ningbo, Zhejiang 315211, P. R. China
5. Photonics Research Center, Guilin University of Electronics Technology, Guilin 541004, P. R. China