Design And Experiment Research Of Two-Cavity Dual-Frequency Yb:YAG Laser

Frequency difference tunable dual-frequency laser has a wide application prospect in laser interferometry,optical sensing and other fields.In order to improve the measurement accuracy,the frequency difference of dual-frequency laser should be as large as possible.At present,the solid gain medium used in dual-frequency laser is mostly Nd3+-doped crystal,which has small fluorescence bandwidth and small output frequency difference.In this thesis,the Yb:YAG crystal with wide emission spectrum is used as the gain medium,and a large frequency difference tunable two-cavity dual-frequency laser is designed.The main contents of this thesis include the following aspects:Firstly,the domestic and foreign research progress of dual-frequency solid-state laser is described,and the system composition and working principle of two-cavity dual-frequency solid-state laser are analyzed in detail.The operating characteristics of a three-level laser system are analyzed by using the rate equation.Secondly,two different modes of mode selection for two-cavity and dual-frequency solid-state lasers are designed,which are birefringent filter mode selection and twist mode selection two-cavity and dual-frequency Yb:YAG laser.Both of two adopt two-cavity structure,and the two-cavity have independent longitudinal mode selection system.Under the action of longitudinal mode selection element,the dual-frequency laser is output.At the same time,the feasibility of the two schemes is analyzed theoretically.Thirdly,the experimental system of single frequency Yb:YAG laser with birefringent filter is established.A birefringent filter composed of PBS and HWP is used to select the longitudinal mode,and 1030nm single frequency laser output was realized.By adjusting the angle of HWP in the cavity,the wavelength tuning of 1.6nm single frequency laser output is obtained,and the corresponding frequency tuning is 452GHz.With the increase of the angle of HWP,the laser output frequency changes periodically.At the same time,the experimental system of single frequency Yb:YAG laser with twist mode cavity is established.The longitudinal mode of the twist mode cavity composed of double QWP and Yb:YAG crystal is selected,and 1030nm single frequency laser output is realized.Fourthly,the experimental system of two-cavity and dual frequency Yb:YAG laser is built,and the power characteristics,oscillation characteristics,frequency difference tuning characteristics and polarization characteristics of dual-frequency laser are studied in detail.The experimental results show that the two-cavity oscillate in the form of single longitudinal mode under the action of birefringent filter.The dual-frequency laser output with different frequency differences can be obtained by fine-tuning the inclination of the HWP in the cavity.The linear cavity frequency tuning is 452GHz,the rectangular cavity frequency tuning is 412GHz,and the maximum frequency difference of the system output dual-frequency laser is 542GHz.In summary,the principle of dual-frequency Yb:YAG laser oscillation is analyzed in detail in this thesis,a two-cavity experimental system is built,and a dual-frequency laser output of 1030nm with stable output frequency is obtained.