1. Institute of Laser and Opto-electronics; College of Precision Instrument and Opto-electronics Engineering; Tianjin University; Tianjin 300072 P.R. China
2. Key Laboratory for Opto-electronics Information Technology of the Education Ministry; Tianjin University; Tianjin 300072 P.R. China
3. Henan Key Laboratory of Laser and Opto-electric Information Technology; Zhengzhou 450052 P.R. China
4. State Key Laboratory of Precision Measuring Technology and Instruments; Tianjin University; Tianjin 300072 P.R. China