Design And Experimental Investigations Of THz Frequency-difference Two-cavity Dual-frequency All-solid-state Lasers

THz-frequency-difference two-cavity dual-frequency all-solid-state lasers have broadly wide application prospects in the fields of laser interferometry,optical sensing and lidar.When a dual-frequency laser is used as a light source in a synthetic wave absolute distance interferometry system,increasing the frequency difference can improve the ranging accuracy.Compared with traditional dual-frequency lasers,THz frequency-difference two-cavity dual-frequency all-solid-state lasers have the advantages of simple structure,small size,easy integration,and large frequency difference tuning range.Therefore,it is of great significance to carry out the design and research of THz frequency difference two-cavity dual-frequency all-solid-state lasers.The main contents of the thesis include the following four parts:Firstly,the domestic and foreign research status and development trend of the frequency-tunable dual-frequency laser technologies have been briefly introduced.The system composition and operating principles of the two-cavity dual-frequency all-solid-state lasers have been analyzed in detail.Through the four-level rate equations and the quasi-three-level rate equations,the operating characteristics of both systems of the Nd:YAG laser and Yb:KGW laser have been theoretically analyzed.Secondly,based on the single-mode selecting principle of Fabry-Perot etalon,two research schemes of both two-cavity dual-frequency Nd:YAG laser and THz-frequency-difference two-cavity dual-frequency Yb:KGW laser have been designed.The feasibilities of the both schemes laser have theoretically analyzed.Thirdly,the parameters of the double Fabry-Perot etalons have been optimized.Based on the small signal gain function,resonant cavity frequency comb and transmittance function of both etalons,the longitudinal mode selection characteristics of double Fabry-Perot etalons in the Yb:KGW laser system and the frequency tuning properties of single cavity Yb:KGW laser have been simulated.The simulation results show that the both etalons with the designed parameters can realize single longitudinal mode selection in Yb:KGW laser system.When the tilt angle of the thin etalon in the Yb:KGW laser system varies from 0.02° to 3.65°,the maximum frequency tuning of the single-cavity Yb:KGW laser can reach approximately 3.6THz.As the tilt angle continues to increase,the frequency tuning shows a periodic change trendFourthly,the two-cavity dual-frequency all-solid-state laser systems have been established and experimentally investigated.First,the characteristics of the 1064nm two-cavity dual-frequency Nd:YAG laser have been studied,including the oscillation threshold,output power,and polarization.When the pump power is 1.12W,the average output power of the linear cavity and the right-angle cavity are 23.4mw and 48.4mw,respectively.By fine-tuning the tilt angle of the F-P etalon in the cavity,dual-frequency laser oscillations with different frequency differences can be obtained,and the maximum frequency difference can reach approximately 148.3GHz.Additionally an experimental system of THz-frequency-difference two-cavity Yb:KGW laser have been established,and the oscillation threshold,output power,polarization and other characteristics of the laser system have been experimentally studied,and the stable oscillations of the 1030nm two-cavity Yb:KGW laser have been achieved simultaneously.