1. Engineering Research Center of Optical Instrument and System The Ministry of Education Shanghai Key Laboratory of Modern Optical Systems University of Shanghai for Science and Technology Shanghai 200093 P. R. China
2. School of Applied Physics and Materials Wuyi University Jiangmen Guangdong 529020 P. R. China
3. State Key Laboratory of Luminescent Materials and Devices, and Guangdong Provincial Key Laboratory of Fiber Laser Materials and Applied Techniques Guangzhou 510641 P. R. China