Design And Experimental Research On Two-cavity Dual-frequency Yb:KGW Laser With Tunable Frequency Difference

Since the first ruby laser was invented in the world,laser has been widely used in industrial production,national defense,medical treatment,scientific research and other fields because of its high brightness,good directivity and coherence.Especially in the application of synthetic-wave absolute distance interferometry,dual-frequency laser plays an extremely important role.The larger the frequency difference means the smaller synthetic wavelength and the better ranging accuracy;At the same time,in order to complete the rough measurement of the distance easily,a larger synthetic wavelength is needed.That means,the frequency difference of the dual-frequency laser is required to be as small as possible.Therefore,the tunable dual-frequency laser becomes the ideal light source in the system of synthetic-wave absolute distance interferometry.The gain linewidth of solid-state laser is very wide,which can generate tunable dual-frequency laser with large frequency difference.It is quite essential to study the techniques of tunable dual-frequency solid-state laser with large frequency difference.In order to obtain the output of tunable dual-frequency laser,a two-cavity dual-frequency Yb:KGW laser has been designed,which is based on the mode selection principle of double Fabry-Perot etalons.The principles of single longitudinal mode selection and frequency tuning have been theoretically analyzed.The characteristics of the longitudinal mode oscillation,frequency tuning,output power and polarization state of the laser have been studied experimentally.There are five parts of main content in the thesis.First of all,the research significance of the dual-frequency laser technology and its research status at home and abroad have been summarized.The basic components,working principle and characteristics of all-solid-state laser have been analyzed.Secondly,a research scheme of two-cavity dual-frequency Yb:KGW laser has been designed,which makes double F-P etalons as mode selector.The single-longitudinal-mode selection and frequency-difference tuning of two-cavity dual-frequency laser are realized by tuning the inclination angles of two thin F-P etalons slightly in two cavities.The feasibility of the scheme has been analyzed theoretically.Thirdly,several sets of F-P etalons with different parameters have been designed.The characteristics of mode selection and frequency tuning with double F-P etalons have been simulated in two-cavity dual-frequency Yb:KGW laser.The results show that the thicknesses of two kinds of etalons are determined to be 1mm and 260?m respectively,the reflectivity of the two is 85%and 90%respectively,the combination of the two can realize the selection of single longitudinal mode;When the inclination angle of thin etalon changes between 2.13° and 2.65°,the frequency change of single-longitudinal-mode laser reach terahertz.The tuning angle of thin etalon keeps on increasing,the frequency tuning of single-longitudinal-mode laser will change periodically.Fourthly,the experimental system of LD pumped single frequency Yb:KGW laser has been established.The characteristics of power,polarization state,mode selection and frequency tuning have been studied experimentally.The results show that not only the oscillation output of single-longitudinal-mode laser,but also the frequency tuning of the output laser can be realized by tuning the inclination angles of two F-P etalons at the same time.The corresponding frequency tuning can be up to 1.97 THz.Fifthly,the experimental system of LD pumped two-cavity dual-frequency Yb:KGW laser has been established.The characteristics of longitudinal mode oscillation,output power,frequency-difference tuning and polarization state of dual-frequency laser have been studied experimentally.The results show that,the system can output two single-longitudinal-mode laser beams by tuning the inclination angles of two etalons in two cavities with a fixed cavity length of 50 mm and a pump power of 4.8 W.The frequency-difference tuning can be up to 1.41 THz.In conclusion,a LD pumped two-cavity dual-frequency Yb:KGW laser with mode selected by double F-P etalons has been designed and analyzed in the thesis.The characteristics of single-longitudinal-mode selection,frequency tuning and polarization state have been studied experimentally,which lays a solid foundation for further research of LD pumped two-cavity dual-frequency Yb:KGW laser.