1. Qingdao Innovation and Development Center, Harbin Engineering University 1 , Qingdao 266400, China
2. Key Laboratory of In-fiber Integrated Optics, Ministry Education of China, Harbin Engineering University 2 , Harbin 150001, China
3. Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University 3 , Shenzhen 518060, China