Design And Experimental Study Of Two-wavelength Single-Longitudinal-Mode Ytterbium-Erbium Co-doped Fiber Laser

Dual-frequency laser has been widely used in optical sensing and optical measurement,especially in the field of absolute distance measurement. When the dual frequenc.y laser is used as a light source for absolute distance measurement, in order to improve measurement accuracy,the synthetic wavelength should be as short as possible, considering that the synthetic wavelength is inversely proportional to the frequency difference of the dual-frequency laser, the frequency difference of the dual-frequency laser should be large enough, therefore it has a great significance to study large frequency difference single longitudinal mode dual frequency laser.Dual-wavelength single-longitudinal-mode fiber laser is a new type of dual-frequency laser,because of the unique waveguide structure, it have the characteristics of higher laser quality,easy of integration and high detection sensitivity, which make it become a hot topic of dual-frequency laser research in recent years.In this thesis, the schemes of dual wavelength single-longitudinal mode erbium-ytterbium co-doped double-clad fiber laser with ring cavity and standing wave cavity have been designed respectively. the fiber polarization beam splitter (FPBS) and double Bragg grating (FBG) have been used as the wavelength selection in proposed scheme, besides, the compound ring cavity and unpumped erbium-doped fiber, which is used as saturated absorber, have been utilized to select the mode of output laser.The research status of dual-wavelength erbium-ytterbium co-doped fiber laser has been introduced, the characteristics of clad fiber and cladding pump technology have been described,and the basic principle of erbium-ytterbium co-doped fiber laser has been analyzed; Based on the theoretical analysis of characteristics of the ring cavity and the standing-cavity fiber laser,the dual-wavelength oscillation principle and longitudinal mode selection method, the schemes of dual-wavelength single-longitudinal mode erbium-ytterbium co-doped fiber laser with ring cavity and standing wave cavity have been designed respectively in the thesis.The oscillating characteristics and power characteristics, which of the dual-wavelength single-longitudinal mode erbium-ytterbium co-doped fiber laser with ring cavity, have been investigated experimentally. Research indicates that the ring cavity fiber laser can steadily output dual-wavelength laser at 1539.90nm and 1550.08nm, the wavelength spacing is 10.18nm,the fiber laser can output single longitudinal mode laser when both the unpump erbium doped fiber (UPEDF) and the composite cavity are used for selecting the longitudinal mode; The threshold pump is 49.36mW, the system slope efficiency is 12.8%, the output power is 27.49mW when the pump power is 260mW.The oscillating characteristics and power characteristics of the dual-wavelength single-longitudinal mode erbium-ytterbium co-doped fiber laser with standing wave cavity have been studied experimentally, the central wavelengths of the dual wavelength laser are 1539.92nm and 1550.08nm, the wavelength difference reach 10.16nm, the pump threshold is 24.8mW, and the system slope efficiency is 9.70%; The standing cavity fiber laser can output dual-wavelength single-longitudinal mode laser when the UPEDF saturated absorber is used in the resonator, however, it is easy to produce the mode hopping phenomenon.Theoretical analysis and experimental study results show that the two research schemes of dual-wavelength single-longitudinal mode double-clad fiber laser with ring cavity and standing wave cavity are feasible, which lays a solid foundation for further research of high power and dual-wavelength single-longitudinal mode fiber laser.